When I grew up my parents were very hot on the way I spoke, and I was always told to speak the Queen's English, my nan was always very well spoken so I was too, comapred to the people I grew up with that is, I don't have a particularly posh or common accent.
I no longer have contact with ym parents and from the age of about 15 have always hung around with people who had more Eastenders style accents, so mine kidn of fell in with theirs I suppose.
Now though, I have moved and my partner is terribly well spoken so coupled with how my parents actually taught me to speak (and probably partly through actually typing properly rather than using the kind of slang I would have used vocally) I find I speak alot better than I did a year or so ago, not intentionally, but I do, as do my children, and now I get looked at strange by people I used to know who think I have 'turned posh', whereas I used to get the immediate 'common as muck' label.
I have always been careful to 'speak properly' as my parents would say when trying to get someone to do something for me, for example a call centre or a school teacher, if you speak properly they do take more notice.
Accents really are a strange thing.