When mine broke last week, it was actually the coupling that joins the four wires together (near the winch).
Get someone to lift the broken corner whilst you wind it up and put a length of timber under to support it, I lifted mine about two foot, so I could crawl in.
From the winch a single cable runs accross the width of the camper, usually boxed in or through the seating.
At the end of this is a square plate where the four cables are attached, this is where mine had broken.
Luckily it was the eye bolt, not the cable itself, I replaced this with a normal bolt with a big washer on the end, slotted through the cable.
Make sure your roof looks level and tension the cable by tightening the bolt.
Took me about two hours to sort.
If it has broken somewhere along its length, it is more difficult.
Try tent valeting services in Bolton, they give great advice and do servicing repairs for all models of Conway.
Good Luck
Phil
July 2010