How old are you? You mention that you have flatmates, but not everybody wants to live in a shared apartment far into their thirties, especially if you would like to find a place for you and your partner. The problem is that housing in London looks like a commodity that big sharks trade like many other long-term investment commodities. Problem is, that's the places where people would actually like to live that you're trading like it was crude oil barrels. How is that even barely sustainable for a city in the long term? Not limiting that by rules of law is a big mistake, but no politicians would be ever called into account for that.