Or Staines. Or Slough. Or Woking. Or somewhere with National Express. You are too London-centric in your thinking.
Some of those areas are not exactly cheap.
MF crew would have to live fairly close to LHR as they will be operating both long and shorthaul trips and sometimes to scheme with minimum rest between flights. Some temporary crew at LHR, on MF terms and conditions, have even spent a couple of nights at the airport because it's not been financially feasible for them to go home as they would lose out.
Sounds very nice.