Biggest lips I've had the pleasure of is Honey / Honeyminx in North Tyneside. She's getting on a bit now, though, and isn't the best looker. Squirts buckets.
Second biggest is mistresslips, again in North Tyneside - Killingworth. Not as big, and not as sensitive down there, but stunning, about half Honey's age, and eyes to die for. Name is a bit misleading, mind.
I'm also a lips man ... but I'd be heading for Killy!