We can’t even agree on what to call a bread roll [0] never mind how some words should be pronounced [1].
My mother was brought up in Liverpool, but her (Irish immigrant) mother hated the Bootle accent so much that she taught her, and her older sister, to speak something closer to RP.
That washed off, and like her I got bullied at school in North Derbyshire for speaking “too posh”. Yet locals in my new home of London clearly place me as being from the North but can’t place where. To be honest neither can most Northerners. I think I’m broadly “South Pennine”, so a bit of High Peak, a bit of Manchester, the odd spot of Lancashire or even West Yorkshire - reflects where I grew up, went to Uni, lived, and socialised with. My partner has a similar accent despite growing up in a part of Manchester with a distinct accent and dialect of its own.
The point is, it’s complex and it’s changing. And it’s not just the UK. It seems to have sped up in recent years. When I hear Canadian voices from 70 years ago, I can hear Scottish tinges. Likewise the US East coast of the mid-20th century had more West Country in it than today.
It was only a friend’s grandfathers generation that could tell what street someone grew up on from their voice alone, and today we are increasingly homogenised - I wonder what “English” will sound like in 200 or 500 years.