30 seconds on Google gives loads of results, including this one at the top:
http://ukga.com/classified/viewcateg...edCategoryId=2
It's also worth going to the cafe / clubhouse at the airfield you'd like to be based at, and looking at their notice board.
Finally, Flyer, Pilot, and Today's Pilot all have sections at the back of the magazine, and probably on their websites, where many shares are offered.
DW