Hello Kev---I renewed my window seals last year on my 490---the origonal grey type are not UV protected, and eventually crack---can't remember where I bought the new (black)seal strip, but doing the job was no problem at all. A bit time consuming certainly. The seal strip I purchased had the mastic sealant already "built in" which was good---I don't know if all seals have this or not---try Broadlane caravans in Alcester ---rings a bell!!---also if you do the job have at your disposal a bottle of turps or white spirit--this will clean excess mastic off the van's body work---and you fingers!!--a good SHARP blade or knife and a staple gun to pin the new seals to the window. frame---hope this helps