They did eventually let us through to baggage reclaim to get our checked bags, but did not allow us to take books or newspapers with us. So that was an hour or so spent waiting by the belts with nothing to do but try the Sudoku from last night's Newcastle Evening Chronicle.
They still weren't giving us straight answers about when flights might be expected to resume, other than to advise us to travel another day (and full marks to BA for making this reasonably clear via the PA system; unfortunately I was travelling with BMI). I decided that there was no way I was entrusting myself to the air, and with some help from colleagues worked out the boat solution.
(To my shame, I had absolutely no idea how long it would take to travel from Euston to Liverpool, and was not certain if I could make it for Birkenhead at half eight if leaving London at lunchtime. For future reference, it is only a three hour journey.)
So here I am, folks. Must do some actual work now but will update when necessary.