http://www.londonpropertywatch.co.uk/average_rental_yield.ht...
Who cares if you are pricing someone else out of a place to live in London? Seemingly nobody cares. The government love it that there is rampant house price inflation. The ride should be good for a while. Wherever you put your money it will not be immune to the next big crisis of capitalism, in London property you will be well insulated.
As well as the return in rental, you will also have a property that will appreciate in value over time. Sure you might have to sit things out when the property market is depressed, but I would be surprised if your $1M flat is worth less than that in 5+ years time even if the whole housing market goes 2008-style again.