I went for a 3 day kitesurfing lessons with the kitesurf centre at Camber. It cost £239 which I thought was pretty reasonable when I researched the other schools.
The lessons went really well, the instructors were really patient (I'm 45 years old and not the quickest of learners!) and offered a lot of information. I had a brilliant weekend and they sorted the accomodation for me as well. I managed to get up and riding after just 3 days of kite surfing lessons!! I was very pleased!
The beach and centre is ideal at camber as its really open. On the kent and sussex border it only took me an hour from london.

I can't recommend these lessons enough, its so much fun and i'm totally addicted. I ended up buying kites from their shop and continuing the sport all summer! Thanks guys!