I know nothing about the play, so I am not comparing it in that way, but I did see echoes of Orton in this - Sloane reminded me of Stings version of Martin (though of course Sloane was about arrogant sexuality as well as being a bad lot, and Martin is obsequious whilst being about the baddest lot there is). Sting appears to be taking cues from Malcolm McDowell as well, reminding me of when 'little Alex' was pretending to be a good boy. I haven't seen the Michael Kitchen version, so I do not know how Sting, not an actor, compares, but I don't think he is too bad.
I do not agree with another review that this is a disaster - I feel that it is atmospheric, well acted (that poor actress playing the daughter!) and strongly evocative of corruption and moral rottenness - Martin is clearly diabolic, I actually feel that this is rather overdone. He hangs around looking for suitably troubled people and finds his latest target, more troubled than most - sexually repressed and frustrated, guilt ridden due to his daughters disability, and his long suffering wife is a devout Christian. Their adult daughter is completely dependent and it appears that her mother does all the care and the housework. There are enough tensions in this marriage for Martin to work his 'charm': introducing even further conflict obliquely.
POSSIBLE PLOT SPOILER
For me the best and worst aspect of the film is the 'miracle' that Martin inadvertently (or is it) performs as a result of the rape. Through an act of evil someone is saved, though not without further cost. But for the more literal minded (I remember a conversation at the time of release) it is distressing to see an act of violence as a cure for disability, particularly in the context of young disabled women being extremely vulnerable to sexual abuse. One has to remember this is NOT a film about disability.