airlines with crew based in LHR
UA
BMI
BA
JAL
ANZ
QF
CX
ANA
VS (Dual base with LGW)
PIA
Airlines with crew based in LGW
BA
ZOOM
EASYJET
FIRST CHOICE
THOMAS COOK
MONARCH
TUI
XL
VS (Dual base with LHR)
Airlines with crew based in LTN
SILVERJET
EASYJET
RYAN AIR
TUI
MONARCH
XL
However chater airlines like the 3 above have temp bases @ LTN so you will have to find that out.
These are all i can think of. Hope it helps