Well, the runway at Birmingham is TWO metres too short for a 764 (2598 meters), but because the aircraft wouldn’t be at MTOW this would be possible. The 767-200ER needs 2400 meters so that route can be operated with that type.
The 757-200 seems a good choice for them, and knowing that Continental likes to use the 752 transatlantic… However, they replaced the route to Brussels with a 764 instead of the 752! This makes it one of the biggest airliners that visit Brussels (Daily we have around 5 767 rotations :o, charters not included).