Before choosing tiles or fittings, the first decision in any bathroom refit is layout — specifically, whether the existing positions of the waste pipe and soil stack can be kept, or whether you want to move the toilet, basin or shower somewhere new.
Keeping fittings on their existing waste runs is usually cheaper and faster. Moving them is entirely possible but adds cost for new pipework, and sometimes affects the ceiling below if pipes need to run a different route.
Once layout is settled, ventilation (a bathroom without a window needs a properly specified extractor fan under Building Regulations) and underfloor heating decisions should be made before any tiling begins, since both affect floor buildup.
