Underfloor and bathroom

We have a tiled central hall, same tiles into the downstairs toilet on one side, and utility to the other side but With different tiles. We would like to put in underfloor heating, having the same floor flow through hall, utility and toilet and that floor then continue into living room. We would also like to redesign the utility room and toilet. Knowing utility room akin to kitchen cabinets would finish with a plynth, I assume you could lay underfloor heating last after cabinet install etc and tile up to and just under the cabinets? But then for the toilet, would we do the underfloor and flooring first and then build the redesign toilet and cabinets on top? Assuming you have to screw toilet into floor and tiling for flooring looks better rather than fitted around? Or is it neither here nor there?