Because I don't have an EU or UK passport, I haven't had the stomach to do a b2b yet. I've always done an overnight. That said, I'm getting a bit bolder this year:

* LHR-DUB-LHR, 4 hour layover between tickets
* PHL-DUB-LHR, arrive at DUB at 08:45, haven't decided how much time to allow between flights, but give that it's an AA flight, I'm not too concerned as long as it meets MCT.

Eventually I'll probably try an SVG or BGO b2b given the lack of passport checks, though I would probably want to spend the night anyway if time permits as both are nice small cities, and I try to make a habit of seeing the places I travel to.