If those communities were moving to London they would be doing fine. The unemployment rate in the UK is really low. It doesn't mean that a job will show up at your doorstep without having to do anything.
I grew up in a coalfield area. I have friends and family who made that move and further afield. It's a big ask for people to uproot their families from their support network and stable council house for a very uncertain future in London. What transferable skills do you think a coal miner had?
UK is not doing well and moving to the incredibly expensive London is not some easy fix you think it is.