Two of ours have been on residential courses run by this company. It's based in Billericay, Essex, but one of the centres they use is in Northamptonshire: http://www.giftltd.co.uk/
Our first contact with them was when we had a letter from DS1's school, but students don't have to be 'put forward' for courses. They seem to have a lot of fun (and DS1 even met the young woman who became his girlfriend on the one he went on after year 11, but I wouldn't rely on the company as a matchmaking agency
and yes, the sleeping quarters are segregated).