I've only come across one pub with a definite anti-yoof policy - the Crown in Old Harlow, where there's a sign in the window saying "No admission to anyone under 25 unless they are with their parents." That's the way! One of the few pubs I know where they had a major refurbishment which actually improved the place. And they like the odd bit of live music too.

Pub can survive the kind of thing Daev mentioned - the old George and Dragon in Epping got taken over by a new chain who gutted it and called the the Firkin and Forest or something like that, and yoofed it up. But now it's gone back to being the George and Dragon, and abandoned the quest to pull in people who aren't old enough to legally drink, and it's not a bad place now.