"To sing songs in your own accent was the advice MacColl gave to all singers, amature or professional - it's always made sense to me"
Agreed, and it's good advice, but MacColl should have done it in private, not from the stage, which is bound to be humiliating for any singer - [ if that's what happened, and I have no reason to doubt it].
Could the discussion return to it's original subject now please ?