Just the other day i mistook a Lancashire accent for West Yorkshire, there just all the same to me.
East Lancs and West Yorkshire are pretty similar TBF.
Somebody once told me that children up to the age of 18 will change their accents to ‘conform’with their friends.
I don’t think it’s necessarily conscious, but some people are more susceptible than others. My better half was born in Central Lancashire, grew up in Somerset, lived in the Home Counties for a good chunk of her adult life, spent a lot of time in London and has been in East Lancs for the last ten years (I think I’ve got that right, it’s hard to keep track. She has a fairly neutral accent but it does tend to flux if we move around the country. Up here people think she’s well spoken, go down to That London and everyone thinks she’s a Northerner. Visiting her mum for a week in Taunton and she comes back sounding like she’s been in the fields on the cider.
My ex was a Welsh schoolteacher, out of term time she’d have a nondescript accent that you’d never place; during term she sounded like Charlotte Church.
I’m similar too I think. Away from home my accent tends to soften (sometimes by choice so that I can be understood by Americans), then when I get home it almost immediately degenerates into hey up and sithee. I’m not as broad as my farmer grandparents were, but can affect it if I put my mind to it. Part of that’s probably just by dint of being educated and learning to pronounce words properly; things like “bath” and “note” are as flat as you like, but things like “Sarah” come out as “Say-rah” rather than “Surr-ah” because, I dunno, it just sounds wrong and ugly otherwise.