We met a family on holiday once who had moved from London to Birmingham. The mother, in a very cut-glass voice, used to say brightly to her young daughters "Talk like Mummy, not like Brummy".
I amused myself imagining the possible circumstances in which her girls would inevitably repeat this in public and embarrass Mum.
Mind you I'm not enjoying the influence of 'estuary' in our household - but the DC tell me that they are considered very posh in the playground so I can't push it too much. But is it too much to ask for the 'l' at the end of words to be pronounced?