In Britain the accent changes hugely if you travel even twenty miles (sometimes less). I don't know much about it, but when I was researching it for something else the British Library website has a map of britain where you can (if you have windows) listen to various dialects.

If you google British Library Regional Dialects, then it should come up. Yep, it does.

I hope that's helpful/ someone else on here might give you more detailed information.