I can't speak for the UK specifically, but Corso has a point that not all rising property value is natural. Sometimes it is indeed artificial. That said, the very investors (banks, speculators, and holders of a second property) that cause the artificial rise are the same ones at worst financial risk when the bubble pops. They're left holding property not worth anything near what they paid for it.
but these cash investors are in it for the long game, its only the morgage stretched that suffer when the bubble bursts, there isn't single property that devalued in the 80's cash that doesn't have a zero or two on its value now.