Active job

Vinyl flooring in new bathroom

We are doing up our bathroom and need vinyl laid. The bathroom is on second floor, polished chipboard. Has had a bath overflowed in here so may need a bit of prep, sanding etc. Not sure if needs waterproofing as well, being a bathroom? We will have a seratone product around face of the bath, looking for advice whether floor goes down first, also not sure if we need coving up the walls.