I think it was Channel 4 (or it could have been Five) which broadcast the series, and there was quite a discussion on the forum as I recall, so I'm thinking 2004.
Sappho x
Was it series from 2005?
If not, you might find it in .
I think you might be thinking of the series discussed here:
http://www.swingingheaven.co.uk/swingers-forum/viewtopic/18649.html
Watched about 3 programmers to do with swinging just previous to joining this site. As out join date states December 2005 I suggest they were all on withing 3-6 months prior to that. Watched the one with the Americans and remember watching another in the UK which seemed to show lots of swingers on their way to meets chatting whilst they drove the car.
Swinging seemed to be the in thing at the time hence all the TV coverage. Sorry cant be much more help than that.