Also on the ABZ-LHR issue..

1) You could go down the night before on BD679 @ 8pm and stay in LHR (2 award seats available)

2) Book the tickets via flybmi.co.uk and pay for them, although if that flight was cancelled and you don't make it to LHR on time ua/us(?) aren't required to re-accommodate you.

PS Denver = DEN