As I said, "Lots of evidence in recent months of house price falls starting and picking up in London/South East, and usually once they start here, price falls spread elsewhere
I don't think it will be like this, this time. Over the last few years, prices have boomed in London and SE, but in other areas, they are still around the 2007 peak, sometimes still below that level. There has been a second boom in London that simply hasn't happened elsewhere.
So more and more people can't even think of affording in and around London and are starting to realise that it isn't the be all and end all and that they can have a more comfortable life, including buying a house, on a lower salary in other UK cities.
Probably adding the uncertainty of Brexit has affected foreign investment and also reduced demand too (eg talk of certain companies moving from London to Frankfurt etc).