We've just booked flights to go out to our villa (obvious plug, I know) and were surprised to see how much cheaper it is to fly from Birmingham than Manchester.
Flights with US Airways from both Birmingham and Manchester stop at Philadelphia where they both connect with the same internal flight anyway!
As an example based on 2 adults & 2 children:
1st to 15th August £3408.40 from Manchester
1st to 15th August £2217.20 from Birmingham
We flew from manchester with US Airways last year and apart from a big delay at Manchester, everything went very smoothly and the US Airways flight staff were great.
This seems like a great way to get over there and save a hefty wedge; which you could use to rent our lovely villa ;)