So to revisit this thread, I decided that I wouldn't be able to do the screed and all around getting the toilet and everything else put in, so I changed plans to Quick-step click LVT planks.
However due to scheduling issues I'll have to leave an access point for the radiator pipes under the floor to be moved, but that needs to wait until the plasterer can do the wall. But I need to fit the flooring before the toilet and vanity go in.
So I have two questions:
1 - what is the minimum sensible width for a piece of plywood subfloor? The sheets are 2400x1200mm and the room is 1665x1700mm, not including a small bit that goes through the doorway. It would be easier to cut one big piece and one small piece, but then the small piece would be 1700x465mm. Is that going to be too narrow?
2 - can I even install the toilet and vanity on top of a floating floor? The toilet would be screwed down and the vanity is a "floor standing" kind that is basically a cabinet resting on the floor. I've read conflicting things about whether this will be a problem. The plumber said the flooring should go under the toilet but I'm wondering if I should not try to put it under the vanity.
3 - if I can't put the flooring and underlay under the vanity, what do I do? Would I need to put some kind of sealant on the plywood under the vanity to protect it from water since it then wouldn't have a waterproof underlay & floor on it? If so what kind?
I really did not plan this project well...