mr fenwicks do some, but what ever you use as the compound for rubbing it with you need vast amounts of elbow grease to!!! oh yeah forgot, loads of patience aswell, and dont expect to do the whole caravan in one day!!!
I use xerapol, saw it reviewed it a caravan magazine and used it myself but with a car buffer/polisher to take the elbow grease out of hand rubbing it.
I recently used T Cut after seeing it mentioned on a previous thread. Worked a treat with minimum of effort - all those light swirl scratches dissappeared and the window was left lovely and smooth and scratch free!!
------------- You only need two tools: WD-40 and Duct Tape.
If it doesn't move and should, use the WD-40.
If it shouldn't move and does, use the duct tape.