Hmm but the fuse is what I said right?

The relay for the interior lights is a tall yellow one if it's a conventional square flat one the only other thing I can think is the cooling fans, can't remember without looking at my fusebox but thinking about it that might be the fan fuse if so it should be 15A, if it were anything to do with your fans the drain would be very fast.

Missed the bit about the footwell lights, yes they should work in conjunction with the interior lights I think, it sounds as if yours are wired independantly as I can't think why else they would be on all the time.

Martin