I've used Autotech a number of times and found them to be very good.
The last job was on a 320i which got stuck in second gear. They tried
to source a second hand or reconditioned box but couldn't find one as
these gearboxes are 'unbreakable' supposedly, so they removed it and
stripped it down and found a broken selector fork. They replaced this
and refitted the box - great job, can't recall the cost but it was,
IIRC, much cheaper than even a second hand box.
Auto Tech Centre
12 Regent St
Liverpool, L3 7BN, UK
0151 236 6966