That is ignoring the problem which is people wanting to live in a specific area, pointing out that there is plenty of space in some other area doesn't necessarily solve it. China has loads of space, people still flock to Hong Kong.
Who said anything about specific areas, or indeed other areas?
I'm talking about the housing shortages and plans for new builds both in areas where they already have plenty of buildings that would be a better option.
demand for space in Central London is still high and empty space in some random commuter town isn't necessarily the solution
The solution to that kind of problem is to move whatever it is in London that people want, to some other town. People generally go there because that's where the work is... or at least the high-paying work.
Part of the reason places like Reading develop and become popular is that companies like to cite their HQs here, or some large facility. Expedia, Microsoft, Hays, Yell.com, Cisco, Harrods, BP, Deloittes, Waitrose, SAP, KPMG, HomeServe, Unilever, ScrewFix, American Express, GSK, the BBC, Accenture and Google all have important (to their business) facilities here and are big-time employers that people want to work for. This brings people here to work and live, which brings better infrastructure and makes Reading better connected for those commuting in... but commuting works both ways, so many in Reading now commute out to places like London again.
That's a big factor in the problem.