I don't think you'll find it went off-air due to contestants losing interest ! It went off air because it cost £250,000 an episode to film. Producing something that is of suitable quality to air on TV takes a lot more effort than people think. Filming through the poly is almost a no-no as most people have discovered trying to film live events, and the lighting requirements for broadcast TV are significant.

Seriously - I really don't think the issue was anyone taking part that lost interest, that's not what makes the show happen.