I'm originally from the North but I lived in London for nearly 40 years. My wife's from London, and our son (now early teens) was born there.
We moved to the Eden Valley in Cumbria about 2 years ago.
Our reasons were varied - we love London (and always will) but mainly got jaded with the very visible and serious ASB and drug dealing in our otherwise perfectly nice area. The most worrying thing for us was knife crime among teens. Don't believe the myth that if you're not involved in gangs you're not at risk.
We were also very fortunate to have had a lot of equity in our property which we decided to make use of. Another factor was fancying a change in the latter half of our lives. We'd lived abroad before but Brexit put the kybosh on that.
Took a LOT of planning - and not a few second thoughts - but we did it. It's turned out to be the best thing we ever did.
The Eden Valley is beautiful, peaceful, full of pleasant towns and villages. Good transport links. The people here are just great. Friendly, helpful and welcoming. Total silence at night. Sky full of stars. Very little serious crime. Amazon boxes left on doorsteps remain unstolen.
Lake Ullswater (and the actual Lake District) are a short, easy drive away. We often take our kayak down to the lake after school for a paddle and a picnic.
We are exceptionally fortunate to now be mortgage-free in a home we'd never be able to afford (or even dream of) in London.
Downsides: It rains. A lot. Way more than the South East. You get used to it. Winters can be brutal in some parts. If you like clothes shopping, you'll need to travel - probably right out of the county unless your thing is Gore Tex or Barbour.
There's not much for teenagers (unless they're outdoorsy), although there are a lot of part time jobs for extra pocket money.
We miss our London life sometimes. But not not very often. It's 3 hours on the train for a 'fix'.
FWIW we often visit Newcastle and Northumberland. It's a great city and a lovely part of the county.