Economists solving the problems the last one caused
Allow essentially unrestricted building in the south east
Builders want to maximise profit - they still need you to pay as much as possible for a house. So instead of building high density low price housing on vacant lots they build estates of million quid McMansions on 1/2 acre lots (just like every US city from Houston to LA)
You now have a suburb that stretches from London to Dover.
The density is too low for public transport to work so everyone has to drive into London
So you need to build 8 lane motorways into London (just like every US city from Houston to LA)
So you need to knock down a lot of cheap high density housing on the routes into the city.
Housing problem cured, transport problem is a matter or the government, can't expect developers to be restricted by red tape and costs of public transport, just privatise the roads - then economics will cure it.