Remers, I don't really care if you think what I say is wrong, instead I refer you to:
UK Border Agency | Advance information on passengers
If you do not provide your details on-line before you fly the data should be collected at the check-in stage. In my experience over the last 12 months (roughly 30-40 return trips between continental Europe and the UK) that data has been demanded by the airlines I have flown with (BA, Ryanair, Easyjet and Air France).