It is, I suspect, a place which you can buy and live in. So, it could be anything from a grand detached house to a small studio flat. Outer boroughs are, I would have thought, likely to have larger properties for sale than inner city ones. The above cartogram is a metric of transaction costs – doubtless if you normalised by number of bedrooms or floor area, the distribution might look a little different although the basic pattern would probably be similar (i.e. central, north and south-west = more expensive).

There are I’m sure cases where a two bed flat in, say, Hammersmith, costs as much as a three bedroom house in Croydon. Is it possible to derive different sets of data for the same cartogram to address those variations?