If it were to be Leeds I'd want to know fairly soon for apex fare; any of the others are quite easy for me, so likely to be in attendance.
I did wonder about Cambridge/Peterborough, but those are rather time-consuming for our western contingent.
I aint ticked Bath yet, but neither have my regular casketeers so that can be done any-ish time.
There, another definitive answer for the list!