Floor tiling labour is priced the same way as walls, at roughly £20 to £40 per square metre. MyJobQuote gives a medium bathroom floor as one day at £150 to £200.
The complication is not the tiling. It is what the tiles are being laid on.
The problem with timber floors
Tile and grout are rigid and brittle. They tolerate almost no movement. A concrete slab provides that rigidity naturally.
A suspended timber floor does not. Floorboards flex underfoot, move with humidity, and deflect between joists. Tile laid directly onto floorboards will crack, and the grout will go first.
This matters here because most South London housing is Victorian or Edwardian with suspended timber floors throughout, including in bathrooms and kitchens.
What a timber floor needs
The usual answer is an overlay: a tile backer board or plywood of adequate thickness, screwed down at close centres to stiffen the floor and provide a stable, flat surface.
The alternative is a decoupling membrane, a matting laid between the substrate and the tile that absorbs small movements and stops them reaching the tile.
Both add cost and both add height. A backer board plus adhesive plus tile can raise the floor by 20mm to 30mm, which affects door clearances, thresholds and, in a bathroom, the relationship to the bath panel and WC.
Some floors also need the joists checking. If the floor is bouncy, stiffening it comes before anything else, because no overlay compensates for inadequate structure.
Why this gets left out of quotes
It is the single most common omission in cheap floor tiling quotes, and it is invisible until the tiles crack a year later.
Ask explicitly what is being laid on the existing floor. If the answer is that the tiles go straight onto floorboards, get another quote. If the answer involves a specific board or membrane, ask what thickness and how it is fixed.
Concrete floors
Simpler, but not automatic. The slab needs to be sound, clean, dry and flat. A self-levelling compound is often needed to correct falls and hollows, and that is an extra material and an extra day for it to cure.
New concrete needs to be fully dry before tiling, which takes considerably longer than people expect.
Tile choice for floors
Porcelain is generally the right answer for floors. It is denser, harder and less porous than ceramic, and it handles traffic and moisture better.
Check the slip rating for bathrooms and kitchens, particularly if the floor gets wet. A highly polished tile that looks superb dry is dangerous underfoot wet.
Large-format tiles demand a much flatter floor. Any deviation shows as lipping between tiles, which is both visible and a trip hazard.
Underfloor heating
If it is going in, it goes under the tile and changes the build-up and the timings. The system needs commissioning to the manufacturer's schedule, typically left off for a period after tiling and then brought up to temperature gradually.
Switching it straight to full heat after tiling stresses the adhesive as it is still curing and is a reliable way to crack a new floor.