Then you are in for the acrobatics ... done better when you're younger, but.
Try to get rent or borrow one of them "wet" vacuum cleaners. Take out the bottom plastics (she can be used without them as well if needs be) lift the carpets by section and try to suck out as much water as you can.
With the same scheme you can move to the "heater" (keep distance between heater and foam!) in whatever downtime you can get. It will alleviate the problem ... do not use anything very sharp, it breaks the foam :-(
I use wooden blocks.

Yeah, might be late ... we do them before fitting them, masking tape to cover the undesired areas and a touch of matt spray is enough to live it up a little.
You can do it mounted, but you need to mask more :-)

Agree with all. Mind you, methods with heaters and so on inside the vehicle are possible, but not that effective.
Best "drier" I have found some far is the Sun :-)
Nothing beats a good afternoon baking, both sides :-)
Any smell just ... disappears!

Nice nice nice!

Please pass some black spray on that crankcase pulley before fitting a belt, I know is a minor cosmetic touch but ...

I had one missing in mine, but after fitting the tow connector all is fine :-)
Hope you get it from someone here, reference is NTC8902 and if available should cost next to nothing.

To the supreme leader of this establishment: could such type of topic be used for a "want/offer/exchange" corner?
No commercial advertising of course, just a means to get, swap, or get rid of stuff in a more friendly manner ...

This fall right into my area ... in our resto/custom projects part of the deep cleaning and "renewal" of interior parts includes heavy washing to get rid of several years of dirt, and the foam soaking is a classic occurrence.
Sorry to be blunt and drastic, but with the proposed ideas will be nearly impossible to get rid of the wetness, you might also incur in a mushy smell that you might never get rid of, or the foam rotting and disintegrating, which I seem to understand is already happening.
The type of cells of the foam are not made to hold water, nor they easily release it ... I've had a car leaking water in (it is a parts car in our wrecker yard) and even after a full summer with little rain the bottom part would still be wet ... I've had another in which I was unable to pull the carpet out to access some connectors, the water turned to ice (it was winter) and it "glued" the foam to the metal :-)

The P38 has a very very thick foam, even by other brands' luxury vehicles standards ... really high and heat formed very precisely to the metal floor. Don't cut it, even if partially missing it still keeps the shape somehow.
The only real solution is to take it out and let it dry, the way Clive did.

Would propping the carpet up and using a heatgun on low allow the foam to dry out do ya'll think?
Propping a piece up and putting heat is a miserable solution with questionable results. DO NOT use a heat gun because the concentrated heat melts the foam, which contracts sharply and makes a horrible smell (don't ask me how I know). At most, you can use one of these small heater like for the bathroom (obviously you need a mains... uh, you guys in UK got what, 110V?). And you need to think to leave it for hours and hours, and you will never be able to get all the foam to dry anyway, since whatever remains in contact with the floor is still ... wet. And besides the time and electrical expense and the risk of melting down the heater directly, you also need to keep the car ventilated from time to time .... ah! and you might end up twisting/deforming the carpet - depending on the "propping element", which will probably ruin it. Been there, done that :-( (all of it including the heater meltdown lol)

What Clive suggests, to do we do it regularly in our workshop with the vacuum cleaner/carpet washer (we use a Karcher SE400, borderline between a home appliance and a pro machine, but okay for regular use).
But only when you cannot get the carpet out, otherwise the best way is to really take everything out, power-wash it with good household cleaning materials, and then use the vacuum to take the biggest drip and then let it dry naturally. Obviously is a nice season job.
This type of "wet vacuum" machines can help you take some of the water in the foam underside the carpet, but it is a long an tedious job. Nevertheless, if you cannot get the carpet out now, and you have access to one of those, you can give it a go for the time being and guaranteed will remove some of the water.

Sorry for the long post. Now, some candy ... here's the underside of the carpet, see how precisely it fits!

And here is being washed .... lots of dirt, it changed actually color

One of my mates in Italy, long time tinkerer on P38s, told me once most shocks past the OE Boge are too firm, which ill suits the spring damping of the EAS. I can't tell ...

You guys are a lovely bunch ...thanks!

wow that is a nice stable!

I think I will also add a note of a different color .... my beauty in green ... but I do not have any current "whole" photos so ....

After a looot of lingering and money wasted (I am gearing up for the "biggest cock up" topic, I think I have good chances of winning a respectable prize there :-/ ) I've finally came across a non-runner (engine no compression) '99 4.6 with a nice body and interior for a cheap price and at only 10km from my workplace and could not let it go ... here it is with my current workhorse taking it "home"

Good info! I've never used the Bosch but now will give it a go!
The original LR how does it fare in these aspects?

Good info! Will switch to 10W-60 when I get the beast out of hibernation ...

My same dilemma ... thicker to hold on more, or thinner to pick up fast? Waiting some wizard to shed light on this :-)

Since the "RR remedies" is no longer available as a direct link - at least I do not know where to find it, we might as well start making our own list of stuff in case needed. Any ideas how to share files which are not photos (I've never done it so far) so we can post and swap guides and "how to" if needed?

Isn't 10W-60 a wee too much hi-tech for the RV8?
I use 10W-60 on my Guzzi ... I did use the Edge EST and later the Motul 7100. Stopped with both as there are too many counterfeit out there and can't trust them.
I use now Marly, I know the importers since years and know can trust the product.

Haven't seen this one yet, but I am sure it is a staple into each owner of a second hand vehicle ...
These are some of the horrors I've met when taking apart stuff that was not working, or not part of the vehicle originally ... this topic is meant to amuse the experienced, to scare the unwary, and in general to promote despising those creating such works of art ...

Attempt at solving battery drain with rallye style on-off switch

by making a hole into the pillar

bodge job on the windscreen washer

just a little bit of dirt ...

you can always evaluate the level of dedication of the diligent P38 owner by forensic examination of the remains of the scuttle panel filter ....

I've never understood what was the purpose of this ...

and finally .... aaah! a classic from one of my favorite characters: the LPG installer! Together with the audio "pro" and the alarm "wizard", the typical LPG installer completes a fantastic trio whose aim in life seems to be only to ruin classic car posterity ... in this particular case, what was the need to drill thru this ... oh well. By the way, using the same cable from the switch I've moved it from "there" to inside the ashtray, without trouble. Despicable people ...

Well, I got more, but now is your turn to delight the crowds! :-)

There you go, fixed! In any case before drilling I wait to see if I can get suitable senders!

Next in line: transmission temperatures!

I've noticed both gearbox and transfer box are fitted with temp switches, which conveniently provide the BeCM temp data of some sort, which conveniently is not provided to the driver except by the "OVERHEAT" message and associated dings and dongs.
Now looking at the ETM from the transfer gearbox comes out from switch X174 the signal, and from the oil cooler is the gearbox temp signal. Both go only to the BeCM and instrument panel. I am thinking both are useless to hijack it since probably are dumb off-on switches, but since SPA design offers a twin temp gauge which looks made to match the green on black LEDs in the P38, why not get both data in.
Now, I haven't, but has anyone else seen an auto temp gauge on a P38? Am I going to be the first one? :-)

I also have dash and HeVAC out and haven't found anything of the sort, which means:

• I have not come across it, or;
• I have not broken it or broken anything that contains it, or
• Somebody else before me has messed around and lost it, or forgot to put it where it goes.
  All three options are likely ... sorry can't be of help :-)

I like this thread! I hope I do NOT have anything to contribute ever! lol! :-)

Not bad! Not bad!
The "leather" has a similar texture to the original one, this is good. If you kept the gaps aligned it will look like it belongs there.
Now you got me to try to make my photo gallery work properly ... so I can post some photos as well

Do as I did ... take your sensor and go around BMW breakers (if any specialized in that in your area), if they know their biz they will recognize it and just snip the cables with the plug. Should cost you next to nothing, nobody wants or needs such parts :-)

Mine has the orangish britpart it was hard-ish but acceptable ... they were leaking tho.
I've fitted the Boge (I did find all fours, you just need more ...luck browsing around) and I fitted but I do not like them (made maybe 500km with them), the ride is very soft and comfy but for towing and my driving I need to go back to something firmer. So they will go.
I got a box with some Terrafirmas (standard) but have not fitted them yet.
Wish I had found Monroes ... Bilstein we use them in our Ur-S projects and they are really the best of the bunch, always.