London might not be "theirs" but if they work there as cleaners / burger flippers / road sweepers etc what do want them to do, pay half their salary every month to commute in from some miserable **** hole like Harlow or Stevenage <enter another miserable **** hole new town built for chavs here> ? HOusing needs to be afordable in all areas for people of all jobs.
I don't think housing does need to be affordable in all areas, certainly not zone 1 or 2 at least. Plenty of other people not eligible for social housing find themselves commuting.