Recently fitted a wolfsburg west one to a bus and the fit was really good and the quality of fabric was superb, with the roof off took about 4-5 hours.
Some of them out there are not a good fit as the patterns they have used are not correct, be warned as some ones that dont fit are the same price as ones that do fit, I'd try Custom & Commercial if you cant get hold of a Wolfsburg West one.
As Graham says - Wolfsberg west ones are excellent, and got mine from C+C
Have some pics of fitting on one of my threads is you want to search, took the roof off and fitted it on the ground, pretty straight forward and happy with it afterwards 8)