If your gonna sell parts try starting up a business on Ebay. A greater number of people will look at stock etc throught that than you would ever see through the doors of a small business.

Its all about having a suitable and readily availible customer base.

Have you thought about tryin to find out about becoming a franchise?? I know it may sound shit but i know Powerflow and Longlife are always looking to franchise and you will also be able to do your MOT idea as you ll need a Ramp etc