I can see both sides of what this thread has led to but lets go back to the original question. If UV is so damaging to the composites why aren't other aircraft affected so badly by this problem? Gliders must spend 90% of their lives in a trailer outside someones house so the few hours they are in the sunshine at the weekend can't really be that bad.
Besides, how many gliders can you count at Booker left outside all summer?
Come on you engineless wonders, dare to be different and get a whacky paint job done on your pride and joy. Mind you, I suppose it might ruin your chances of a subtle getaway when trying to escape after ruining a farmers crop.