If you have ?300 to repairs the car AND lower it, I would suggest a 40mm set of lowering springs and a DIY roof from ebay. A few people have had a go with these and seem to have found them relatively easy and a good product. If replacing the roof is not neccassary, or you dont want to do it, then try Halfords cabrio repair kit. Source some mirrors from a scrap yard, or search ebay again (the mk1s friend). Or put a request out to an internet based scrapyard.