UK has the smallest sized housing in the West, for new builds anyhoo. In London it would be even worse.
818 sq ft=76 sq m. It's halved in size since the 1920s.
http://shrinkthatfootprint.com
http://i3.mirror.co.uk
The average size of a new build one bedroom property is 46 sq m, or the size of a tube carriage:
https://ichef.bbci.co.uk