For starters, we, the British are sexually repressed as a nation and thus (even if they genuinely would choose sex) would never admit that they want 'it' (at least not very openly anyway).
Secondly, we are talking about PS3 owners who by definition would also be gamers. We all know the stereotype about gamers (we'd rather wank ourselves to a photo of Lara Croft or Tifa Lockheart than risk humiliation by interacting with these 'female' creatures) which in turn may have let to a certain expectation by the researchers.
Finally, what are the chances that they chose a handful of people who have never been laid (even if they're in a relationship) or a otherwise not sexually inclined?
You should be wary of statistics since they don't really mean anything unless they're put into a certain context.