The break-up of the states in the UK. There will for sure be a second Scottish referendum as all regions had majorities for remain. Scotland will leave. Wales will stay for the longest probably because they pretty much all went for Brexit. Northern Ireland mostly wanted to remain in the EU but they will leave this and be the only country in the UK with a land border to an EU country.
In terms of immigration, the Leave campaign suggested that they would reduce immigration levels but in actual fact never explicitly said that (or meant it). They proposed means to control immigration, pick and mix those who we want.
Personally, I think if Britain became more federalised it would function more efficiently: in the north the Tories never win, in the south east the Tories always win. With more federal regions in Britain, more popular local "governments" would have more control to fix issues that the opposition wouldn't care to fix.
London - well... It's such a powerhouse housing parliament and the vast majority of all the political control of the U.K. and of course in the City, a global financial hub.