Colin,

I've just had a look in the Industrial Exchange & Mart and have a few numbers. I can't personally recommend any but a phone call should enable you to form an opinion.

AM Repair service 0800 093 2419
Bulldog door services 0800 389 1371
P&K 01204 667703
DP Industrial 01142 889464

These all do delivery and installation if required throughout UK.

Just a word of caution; if you have the glazed type they don't roll up on themselves like a conventional door so you will have restricted headroom inside the door - like an up and over garage door. Secondly, I wouldn't bother with fully automatic operation as you have to have light beams etc for safety. Ours just have two buttons with cam switches to stop at top and bottom.

Lastly, with a conventional type, you can cut down a secondhand door and make it narrower - experience speaking!!

HTH
Richard