RRR Chesterfield is too far for me..( Banbury )
Had a thought today ( like you do )…Remove the floor from the bathroom, put a decently thick polythene sheet on the rafters, replace floor. Let the joists dry out from underneath via the removed kitchen ceiling. This way you, Mrs RRR and the pink one wont have to do without a bathroom.
If the floor-boards are solid timber then there’s a good chance they will dry out ( without ply etc. on top ). when they do re-fix. I, personally wouldn’t re-use any ply or chip-board that’s had two weeks of saturation.