Forget the car the BMW repair came from....but had the same trunk mounted battery setup as the mini....same parts...box was just a different color..
You might be able to get some parts...maybe the best...new or used from waymotorworks in Atlanta....he usually has a few r50/53 he is parting out....also a sponsor here, and a factory trained mini tech....

 

Not all of them do. Those that can are promoted and advertised as such. Some clear engine/emissions codes but not ABS/airbag codes.

A long ways down my list, but the http://www.bavariantechnic.com/buy.aspx appeals to me. I don't have an ABS light to clear, and I'm sure there are less expensive options if that's all I needed to do,

 

Glad your on your way to getting it sorted out.