Phoned Trev- he suggested chuck a can of WD40 in it, which worked, access gained and got home.
It became evident that the lock was worn or something had failed in the mechanism. The lock was duly taped off and I used the boot or the passenger side to lock/unlock.
Finally, decided to fix the damn issue. So, preceding the how to guide, there is a point of note in this thread here:
http://www.e30zone.net/modules.php?name ... c&t=232638
There was no 'access' to get to the lock area. Now its been floated that its necessary to remove the window mechs, I couldnt do this as the previous bodger had superglued them to the armature. Note coupe doors may be different.
So, plan B= Malcolm+Angle Grinder created an access hole.
There is a guide here, note its American:
http://www.billswebspace.com/BMWE30Door ... ebuild.htm
So this is the UK version
Remove the lock indicator by unscrewing

Remove the door handle surround by sliding to the right

Remove the two screws in the arm rest

Remove the electric mirror switch


Remove the final screw in the recess behind the mirror switch

Pop the door card off
Carefully remove/roll up the membrane from the door. Mine was already missing so I replaced when I refitted everything.
Now this is where I needed the hole in the door. At the back of the door, if you have access, you will see the microswitch, lever and horseshoe retaining it. In the way is a black plastic shield, which prevents the lock mech being lifted by a coathanger/other implements.

The bodge tape around the hole is to prevent me repainting the door in arterial red...
The horseshoe is sat on its side, on a UK drivers side like a 'C'
To pop it off, a long screwdriver levering it to the front of the car will see it ping off into the recesses of the lower door. Fish it out, you will reuse it.
The lock and the microswitch plate will now be free, the lock will twist and turn out the door side. The microswitch plate will stay more or less in place.
Once the lock is out, you will need to pull it apart, to find out what went wrong and to rebuild it.
From all the locks I have seen, if they go wrong its not worth a repair job, as the parts fail properly. Small components are very difficult to repair and, more importantly, the lock repair set is currently £21.47 inc VAT direct from Stealers.
Soper of Lincoln got me one in two days, delivered to my door. Part no: 51219061344 (note this is for my 316i saloon, sheck yours in OEM part cat before ordering)
The kit:


You need to spilt down the old lock, to determine your key combination. Do this by tapping out the rear dowel with a nail of correct size.

The lock will now slide apart. Its worth keeping your key engaged in the slot, to prevent any tumblers falling out of place. If this happens you will be unable to rebuild your lock to your key.
When you have your lock to this stage:

You will note there are 11 tumblers: 6 on one side and 5 on another. Open your bags and note there are different tumblers too:

I then laid paper out, to disassemble the main barrel.

I noted down the numbers on each key (not complete here as I dont want you lot knowing my key configuration, its my scrap...) but you get the idea. The guides do not ping out in all directions as the springs are pretty shagged.
Note from this picture that the two innermost followers to the car (2 and 3, and the ones opposite un-numbered in the pic) are a certain type, with a different profile to the others. With this laid out, I was then able to start to rebuild a new barrel, with correct pins/followers in place. Grease as you go using the stuff supplied. Insert a new spring into each hole (11 in total).

You should end up with something resembling this:

I then rebuilt the rest of the lock using new parts from the bag. First:


Then:

Note orientation of overall lock and bits fitted- you will get it when you do it as it falls into place when its lined up correctly.

Next:

Again, note spring location. This part above the spring fits only one way, into a U shaped groove.

Insert the main barrel, with key in place. The new followers will take some time and wiggling to get the key in, especially on the last two 'different' followers. Dont worry about this. ensure you grease everything again and slide it on in.

Armature next- note new ball bearing replacement. Grease this well and it will sit in the right place. The armature then slips into place, with the bearing moving down a channel in the middle of the spindle.




Then the final fiddly bit, the last remaining spring and armature. Mine did need a little tap to sit well. I refitted the dowel pin then used needlenosed pliers to fit the spring. See pictures:



The only snag on this bit is getting the final stage to engage with the spring fitted in the early stages. Arrowed for clarity.

Reassembly is then completed by popping the pin back in:

Its prudent to test movement/key operation.
To refit the lock, its a reverse of removal, however a damn sight more fiddly- you need to coordinate the microswitch plate, the new lock, the actual locking forks inside the door AND get the horseshoe back on. Its possible but you may benefit from a second pair of hands, if only to keep fishing it out of the bottom recess of the door.
Re fit all trim and stand back, amazed that you dont have to walk to the boot to open the car up anymore.
Enjoy, and errors or omissions please add. Thanks to Malc and Trev as always.
Stu





