Firstly you could never use Woodford as for each movement there you lose one at Manchester
It`s not just the runway that constrains or adds movements its the taxiways as well, Heathrow has many exits and their airfield layout is very different from Manchester
Gatwick gets more off one runway as does Stanted due to one very big factor, the mix of aircraft as has been mentioned many times before because Manchester is the only one that has a large number of Turboprop and smalljets
(EMB145, CL65 etc) mixing it with a large number of wideboy causing big gaps to be provided
Heathrow will have fun when the A380 starts because a very large gap has to be built in between the following aircraft ( 12 miles I believe at first )
G-I-B