In line with their bmi heritage I thought for a moment this was a trick question and the answer was going to be none. bmi sometimes ran promotions for routes that had already been scrapped.
I can think of two:
MAN-EDI
NWI-ABZ
I suspect there's also:
MAN-ABZ
I've just looked and I didn't get them all, but I won't spoil it for anyone wanting to guess the correct answer.