DIY Bathroom subfloor, what's the right way?

Bought an old house where the bathroom is in serious need of re doing. We're in London ish so with the quotes we've been getting I'm starting to think about doing it myself apart from the electrics

The floor has some knackered laminate that we want to get rid of. Underneath I'm expecting the floorboards to not be the most even.

I'm happy to use brand name NoMorePly™ or whatever is best as a tile backer board but I'm not sure of all the layers that have to go in between, or the adhesives needed to account for wood movement etc.

What's the correct way of building and waterproofing a bathroom tile floor on top of possibly wonky floorboards? it'll have a bath, so not a wet room