Sale Yamaha might be able to recommend someone.
I'm sure there used to be one in Urmston called Sherwin something or other. Used to see folk with it written on yellow vests. Don't know if they still exist. Will do some asking
Edit:
Found them in the Mellow Sages:
http://www.yell.com/ucs/UcsSearchAct...ston&x=48&y=12