Hi.
Although not that local to you I found a company called Protective Textile Co. at Chessington, west of London to be brilliant.
They made a complicated cover for our boat at half the cost of other quotes,
It was in the best quality material, made in less than two weeks, ( whereas I had been quoted up to three months by others). They will send them out to you too.
They made mine absolutely exactly to the plan I sent them. I marked all the measurements, including zips, eyelets, fasteners etc on a scaled drawing, and it fitted perfectly. The quality of workmanship was excellent. and the price astonishingly low.
They make covers for all sorts of equipment and vehicles.
Check out their website; www.protectivetextile.co.uk.
Cheers. Mick