A lot.
I moved from Lancashire to Oxford working for the NHS, I was put on the higher pay bracket plus advanced the 3 years for my experience. This was in the 1980s.
Everything I wanted I could get in Oxford, things like a trip to the theatre, I could just buy a ticket and get there on the bus. In Lancashire it would have been an overnight stay in Manchester.
I had a discussion with another member of staff about the phrase, "there are no jobs" in Oxford that meant there were no decent jobs, that people could always get a few hours in McDonalds. In Lancashire it meant McDonalds got 50 applications for one job.
Better and more frequent public transport.
For the cost of travel into London you can visit a number of museums for free. Outside London they are few and far between. That means school visits are also easier to plan and also cheaper.
Charity shops are better. Well have better clothes, curtains etc. I got ball gowns in Oxford.
It's generally warmer.
Access to specialist hospitals, children's hospitals are very spread out, Glasgow, Liverpool, Birmingham and London. I may have missed a couple but it doesn't cost as much to get to them if you are in commuting distance of London. And yes I know you can get travel expenses refunded if you are poor but you still have to pay for the travel first.
Many parents have to take a day of work to get their child to a specialist hospital.
I don't know what happens on Scottish islands, travel to a children's hospital must involve a flight or a long ferry ride.
It's not just the North of England though, Cornwall, Scotland, Wales all have similar problems.