Used to fly at Parham, in W. Sussex, and there was useable wave several times a year. Usually it was in a SE to S wind, and it never got very high, best I ever got was an hour creeping around at min sink at around 3500' just outside the Gatwick TMA. Even saw stacked plate lenticulars over Petersfield once, although I was on the ground at the time....
Cheers
John