I'm a specs wearer myself... and they let me fly a helicopter!
The best thing to do is take a look at the CAA blurb on it here:
http://www.caa.co.uk/srg/default.asp
In there you'll find all the requirements, medical and otherwise. However you may, like me, need to get an optician to translate most of the eyesight requirements for you.
If it helps, I consider my eyesight not brilliant at all, yet the CAA says it's fine as long as I wear the correct specs (and fly with a spare pair).
Hope it helps...
Andy