London SMG servicing

[Nightshade]

I've got a BMW E46 M3 SMG which is playing up. Keeps popping into neutral when the car's stationary and warmed up. I've tried the resistor fix but didn't help, so I need to get it looked at at a specialist.

I'm living in Clapham SW London. Anyone know of a good London-based BMW specialist garage that is knowledgeable on SMGs? Ideally I want to find someone who will properly diagnose the problem in case it's just a small part at fault, rather than just say I need a whole new SMG unit!

Thanks.

[Nightshade]

Thanks Schermerhorn but I already tried that

[Nightshade]

Thanks so much guys that's really helpful! CPC probably sounds like my best bet, my brother lives in Amersham too.

Yep I've tried slamming my bonnet, I've had to do this a couple of times already when the gear indicator would flick between a few gear numbers, preventing the car from starting. Now you mention it, I wonder if a faulty bonnet sensor could be related to my 'dropping into neutral when stationary' issue.

Failing that, from a bit of reading it could be the gear position sensor, SMG fluid temp sensor or compression spring. Hoping CPC can help diagnose this for me. I'll let you know how I get on with them.

Seems like there's a lot to go wrong on these SMG M3s...

[Nightshade]

Sorry what's DTC?