I wonder what percentage of BA passengers on the London routes don't transfer.
Not a lot in my experience certainly within the last 12 months. Have sometimes walked down the long tube by myself.
...and while we're on that topic, why is it that Dublin Airport doesn't have a dedicated exit for UK passengers?
It doesn't even have dedicated for returning ROI pax either, LOL. They have to queue up like everyone else. In T1 anyway. Don't know about T2 as I never use it.