The first thing to do is to discuss it with your CFI and see what sort of glider he / she is willing for you to own - if any. One presumes you have Bronze plus XC endoresement and have trained on glass gliders.
My ARC renewal was £100 plus the BGA fee, but it was done by an inspector at my club. It saved a lot on travel as well.
Whatever you buy, make sure the trailer is sound and roadworth. If it isn't you could have an epic trailing it and you will also find a shortage of people willing to collect you from fields.