Through the screw holes that secure the plenum to the bulkhead and through the pollen filter housings. Make sure the seals on the pollen filter housings are good and not letting water in there (wet pollen filters is a good sign it is getting there) and take the screws out that hold the plenum down, squirt RTV under the screw holes and fit new self tappers.

It's only a 5A fuse so maybe drowning the back of the socket in rainwater was enough to cause it to blow?

Check fuse 33 (5A) as that is the one that supplies power to the OBD socket so runs the Nano as soon as it is plugged in.

So the question really isn't why does it suddenly cycle on for a short period but why does it stop in the first place if the pressure and thermal switches don't change state? My understanding is it should run until the pressure switch changes state so it stops and then only start again when the pressure has dropped. It is inhibited at certain times though which may prevent it from reaching full. Before I changed my compressor mounts so I can no longer hear it, I noticed it would sometimes run when sitting at a junction with the brakes on but stop as soon as I started moving.

As long as the thermal switch stays normal, as you say, it isn't a thermal issue so the only thing left is the pressure switch. IIRC pressure switch state and compressor state are on different pages on the Nano screen, so you can't easily see if the switch changes state at the same time as the compressor kicks in. It might be worth hanging an LED across the compressor so you can easily see if they coincide. That would suggest a lack of hysteresis in the pressure switch but as you have two that are both doing the same thing, that doesn't make a lot of sense unless that is how they go with age? It should be closed at 140 psi and not open until it drops to 120 psi.

Taking them off isn't a problem with an angle grinder and 1mm cutting blade. You just slice lengthways so the two halves of the nut fall off.

Yup, thinner spanner (or attack the one you have with a grinder).

The NNN100660 should be a straight swap for your NNN100600 which is the one used with SAI, you'll just need to copy over the code as detailed earlier. I suspect they are all very much the same just with different firmware depending on whether you have SAI or not. No mention of a different one for auto or manual but if they were different, you'd be hard pressed to find one for a manual, a V8, particularly a late model, with a manual gearbox is a bit into hens teeth territory.

I've actually got a NNN100660 that was bought to try to see if it cured a problem on another car that is from a 1999, 4.6, automatic and is a known good one. If you don't find one, drop me a PM as both my cars are GEMS.

I'd only put a link in as a get me home measure, I once drove through a blizzard at night sitting inside a sleeping bag due to a failed driver's side blend motor, not a lot of fun.

Genuine O rings are cheap (about 3 quid each last time I bought some) and changing them isn't the arduous task that many seem to make out it is. As you say, no point in complaining about it, just get on and do it. You'll have less coolant soaked into the carpet to deal with too.

Draught excluding door foam strips from B&Q. It comes on a roll and has sticky stuff on one side and a foam on the other, much the same as what was in there originally.

Yes, if it will go to the floor without pressure in the system, that would suggest air in the manual hydraulic circuit. Looks like you're going to be bleeding it again....

It may just be that your new modulator isn't as gummed up and partially seized as the old one and now you have a pedal that feels as it should have done all along.

RPi did buy a load from Marty so it will be a good one.

I doubt it would make a difference who has owned it, although it is believed it was owned at one time by Brad Pitt who gave it to Jennifer Aniston. They only built 6 Linley's and only 1 in LHD, the one spoken about here Of the other 5, one was stolen and disappeared and the others are all accounted for. See https://howmanymade.co.uk/2016/10/31/range-rover-linley/

When Marty started to offer these he had them made to his precise specifications by a supplier in China. Unfortunately the minimum order quantity was in the thousands but he went ahead anyway and sold batches of them to other resellers as well as selling them direct from his own website. I suspect all of those being advertised on eBay at the moment are from his batch whereas earlier ones may well be ones intended for something else that were close enough to fit but may not work perfectly.

My mate Danny followed Marty's instructions and fitted one which worked perfectly first time even though he does seem to have 10 thumbs. So if he can do it, anyone should be able to......

Knowing the prices some have paid for what I would only describe as 'very nice but not perfect' examples, your one of a kind should fetch 6 figures easily.

Is the pump running when the ignition is turned on? Insufficient brake pressure is the most common cause of Traction Failure.

Years ago all cars had a tap that was operated by the hot, cold or somewhere in between knob or slider which simply regulated (not very well in most cases) the flow of coolant through the heater matrix. For the last 20 years or more, nearly all cars use a full flow system where the temperature is regulated by altering the amount of air that goes either through or around the matrix. That way blend motors can be used to constantly adjust the temperature electronically. In my fleet, as well as the P38s, I've got an early 80's car that uses the tap method and that is pathetic as you can never shut the flow off completely so no matter how hot the weather is so it is windows and sunroof open all the time. Then I've got one from the early 90's that uses a sort of half and half where it has a tap but adjusted by a little electric motor with feedback to tell the controller what position it thinks it is in (mostly, but it is Italian and we all joke about Joe Lucas the Prince of Darkness but I think he was taught everything he knows by the Italians....).

The only way to stop it circulating is to link the two pipes that come from the engine to the heater matrix pipes at the bulkhead so nothing flows through the heater.

Did Gearbox Fault appear immediately the car was started? Did the starter struggle to spin it over? If battery voltage drops below 10V at any time, especially during cranking, it will bring up the gearbox fault message and put the gearbox into limp mode. Limp mode will only use third gear if the fault is detected while stationary or only 4th if detected when moving. This is almost certainly connected with the misfire which is likely to be caused by the crack sensor. If it is to be replaced, ensure a genuine Bosch is fitted and not aftermarket.

Earlier GEMS used two separate temperature sensors, one to drive the dashboard gauge and another to report to the engine ECU. It is the latter one that OBD will show. The Thor uses a single sensor that is actually two in the one body to carry out the same functions as the two separate ones in a GEMS. For some odd reason a bad earth will cause a high reading and not low as you would expect.