There's Noel Butler @ Autokraft, located close to Earlswood / J4 M42 tel 01564 703434, comes highly recommended on numerous forums. I've used him a couple of times and been very happy with the service.
I use Autotech Warwick for my E86.
Andy the owner specialises in BMW and is an ex BMW technician and has deep knowledge especially for Z related issues & mechanics.
http://www.autotechwarwick.com/
Another endorsement for Autotech in Warwick, used many times over the last few years for Z3, Z4, 1 Series and more recently Audi A3.
I believe Ant is slowing down a bit so it may be a longer wait that usual.
There's Noel Butler @ Autokraft, located close to Earlswood / J4 M42 tel 01564 703434, comes highly recommended on numerous forums. I've used him a couple of times and been very happy with the service.