I've definitely seen two of the contestants - the guy in the floral shirt and the young woman - in quiz shows on TV before, but which ones? Univ Challenge, Only Connect, The Chase, Millionaire?
Google finds that someone called Alan Gibbs did well in 'Fifteen to One' in both 2001 and 2002.
An Alan Gibbs also won £125,000 on 'Who Wants to be a Millionaire' in June 2005.
It's a fairly common name but, given that the same people do tend to turn up time and time again on quiz shows, I'd reckon that it's probably the same person.