I've just thought that another reason prices have gone up is computers - people need less stuff. The generation having children now don't have boxes of books, or toys or clothes - my generation used to keep things for years as purchases were more precious/rare. This generation can buy what they want fairly cheaply and so are less attached to objects.
Children have different needs - as a SAHM I had all the paints and easel, craft kits, mini climbing frame - nowadays most children go to nursery all day, then preschool then school and just don't need the stuff that we did. By the time they reach 5 they are doing most of their playing on screens - that's enough entertainment often (not being snooty about it, it's often great and as good as other forms of play).
Adults have kindles, macs, everything they need. Entertainment can be done in good restaurants and bars, no need for a big kitchen. Things are so different in that sense and we live more like the Europeans do now - in small flats, living our social lives outside the home.
So people just need less space. All the London homes are being divided up into flats. Where I grew up is long gone that way and I can't afford to live there. Nearly everyone my dd went to school with lived in a flat.
So although there is a housing shortage I think homes are just different now and you have to be prepared to pay now for a flat what previously you would have paid for a house. I believe this has certainly added to the housing bubble - perceptions of a 'home' are different, just as the dual income family changed the game in the 70s and 80s, this lifestyle change is fuelling it now.
Now my dcs are older, if we shed our old books and things-that-people-used-to-keep-in-the-old-days we could live in a flat too.
Having said that, I wouldn't want to live in central london now - it is full of temporary stay residents, either foreign investors and their staff, or foreign professionals on contracts. Lovely buzzy vibe, but not much real community for families unless you want to make friends with people who will be leaving in a couple of years time.