5k seems absurd, though there is a big differential in the UK between those who own a house and those who do not. If I lived in London, 1e6 GBP would be necessary for housing alone, a ridiculous sum compared to the average wage.
Do you have a large family or a need for an enormous space?
London's expensive, but it's not that expensive. You can get a nice, but not huge, apartment in a central area for £400 / week which would work out to £20K per year.
Source: this was true as of 2011 when I stayed with friends in a 2BR apartment paying exactly that.
I do live in London, and while it's expensive, I can't see how you could need £100k annually simply for accommodation. Unless you have a very large family to support too?
