some things to bear in mind;
you should not tile direct onto floorboards (boards will move, tiles will lift or crack, the way round it is to screw something like marine ply to the floor screwed at 8 inch centres then tile
how ever this causea a rather tall problem, say the marinne ply is 10mm thick, the tiles another 5mm your floor is now 15mm taller than it was, bath panel now wont fit.
not to mention what are you going to do when you need access to the pipes (alterations, leak)
i suggest lino, or stick down tiles, as they are thinner, we opted for lino in bathroom stick down tiles in kitchen