Beach is always best, has to be said, just dont get the time to do it very often! Water is my next thing to try with the kite, just tracking down a board...
And if you're in need of a water fix closer to home, you can always hit the cotswold water park over at South Cerney (Cirencester way). They've got a cable-ski which isnt bad. Never tried a kitesurf board on a cable, but I guess it's very much like wakeboard. I've seen a bloke ride the cable with a surfboard, so I dont think it'll be a problem...