We are blessed in the UK with some of the best sailing locations in the world, if only it were a little warmer!
To answer your question better it would be best to know what kind of sailing you want to do and where you are based.
I will assume you want to go Catsailing, on the south coast there are a number of clubs from which you can sail to or around the Isle of Wight, such as Calshot or Stokes bay, another great location is Mumbles in South Wales.
A good resource is
http://catamaran.co.uk/Club_Directory.htmlAll the best
Gareth
