For this particular one I would ask your local tile merchant (not tops
tiles or the likes... a proper merchant). All I can say is that PVA
will do you no good. Bitumen is already water resistant, so no point
worrying about sealing the floor.
My gut reaction is that you are OK going straight onto Bitumen since it
can also be used as a primer for gloss paints etc. Check however that
it is sound and that no areas are lifting from the concrete.
Why not lay a tile and leabe it for a week and see how solid it is.
After a few days you would still expect it to lify easily, after a week
it may lift, but not easily.
(NewArk Traditional Kitchens 01556 690544)