tell me something

If you were to fly from North America to end up in Leicester, which airport would you choose for best economy? I am not excluding ones with a substantial train or bus ride involved, so long as the expense doesn't negate the savings.

Tell me something else

So if I'm going to be in the East Midlands and I can choose any time of year and my time constraints are few, which UK science fiction convention should I try to schedule around? Why?