Well, it wasn't quite like that. "Accents" or more properly "dialects" vary quite a bit all over Britain.
They're mostly more accents than dialects these days, sadly (you can blame mass culture for
that). And once upon a time, more than that really. The distinctive words don't get used so often, even where the accents remain strong.
One thing I always find very sad is the death (within the lifetime of my parents, not even my grandparents) of the traditional calls to animals; they were probably older than almost any English word still in use.