Hi,
I got my roof from the following address
http://www.uk-motorcaravans.co.uk They cost around £700 for self fit, but if you get it late season, they will fit it for you for another £50 while you wait. At that price its not worth doing the job yourself. Just get a coffee in town and three hours later pick your van up. The company are called leisuredrive and they are in Bolton.
Good luck,
Ness