On my new (to me) P38 the barrel of the drivers door lock started spinning round and round, and then when I finally managed to persuade the key to come out the barrel slid almost all the way back into the door just by touch. I have been fortunate enough in the past not to have to familiarise myself with door anatomy... so, what will have failed? is it just a circlip fallen off inside? PO supplied a RHF door lock in a box of parts, so I suspect the lock was replaced but something was forgotten/ not fitted properly.

This is going to be painful... The lock barrel dropped out and is at the bottom of the door now.. I can see the rod through the round hole, which still has the metal work attached...
On the up side the battery is not connected and the door was locked manually, so the becm cannot make life more difficult for me....on the down side I wd possibly have been able to use the remote to open the door if the battery was connected....

Wd the door open if I manage to pull the rod up? And what kind of tool wd allow me to poke through the hole and lift the rod?

Or alternatively I cd go down the route of removing/ breaking the grille,popping the bonnet and reconnecting the battery...and hoping that the fob wd still be synched

Not sure who reassembled the lock/ what corners were cut...but thats in the past now

Any ideas?

If you can see the end of the rod, you should be able to get something (thin screwdriver, length of thick wire or, ideally, a very thin pair of long nosed pliers or a strong pair of tweezers) in through the hole and move it. Having just checked a door latch that I have on the bench, it appears that it needs to be pushed down to unlock (which will also lift the sill locking button).

Ta

Pushed it down and open it popped. So someone had switched the barrel over in the outer door lock but not retained it with either a roll pin or screw, so the barrel pushed straight out. I'm guessing there is another bit sitting in the bottom of the door though since after a rebuild a turning key does not turn the cam on the outdoor lock

yep, the barrel goes in a sleeve, which then has another collar on top, to lock to the cam on the outdoor lock. found a collar sitting in the spares box... all good now. Thanks for the key tip - push down, not pull up : o)

I've got odd bits and pieces that may come in useful one day, but how come you had a collar if you've never taken a lock out before?

Sorry, I was imprecise with the "spares box" reference... The "new" p38 came with a box of old bits, including a couple of dismantled handles... there was a collar in there... and later I fished the other one out of the bottom of the door : o)

All is well that ends well :-)

The "box of bits" that comes with a new (used) car is invaluable to understand what the PO was trying, or succeed at, doing.
Always very indicative ...

How true 😄