Sorry to hear this Sam, it is infuriating isn't it. You need to get on the phone to Stratstone and stop them doing any work on your car, that price is a disgrace. You will end up with a recon box whether you use a main dealer or not, as production of the midlands box ended some time ago. Use a site sponsor as they will be much better for you price wise. As you are probably aware you'll be able to find plenty of feedback on here about any of them.
If you are considering 1320 autos then you may be interested in their 5 or 6 speed Getrag conversion which will give you a much more reliable box. Thread is below.
Hope it works out and doesn't hurt the pocket to much.
http://www.mini2.com/forum/faults-fi...onversion.html