A friend of mine has just started with this firm, based Solent way and office in Manningtree, Essex.
I have no connection except he is a very effecient young trustworthy guy.
Elite Yacht Covers. Noah Di Paolo. Email: noah@eliteyachtcovers.com. Google Search
It would be quite a nice project to cut and sew your cover your self. However it is the strength and longevity of the cloth that matters. It will inevitably flap in the wind and this can destroy lighter cloth. On the other hand a proffessional might be able to buy the cloth in bulk so much cheaper than you as to cover cost of making it.
Do consider type and number of attachments around the edge. Very critical. ol'will