A bathroom is mostly a question of where the water can go, and in Daventry the answer depends on which half of the town you are in.
On the estate housing the soil stack is usually internal or on a rear elevation nobody is protecting, so a bathroom can be moved with a good deal of freedom. In the town centre conservation area an external soil pipe on a street facing elevation is a different matter, because the Article 4 direction already controls the appearance of the frontage. Behind the building line there is far more room to work, which is where most relocated bathrooms end up.
Floors are the second constraint. Upstairs joists were sized for a bedroom, not for a filled bath sitting on a tiled floor. Where a waste run means notching or drilling them there are permitted zones, and the wrong cut in the wrong place is both common and serious. We will move a fitting a foot rather than cut a joist where it must not be cut.
Ventilation gets treated as an afterthought and then causes years of trouble. An extractor discharging into a roof void puts the moisture straight back into the house. We duct it outside.
Tanking is not optional on a walk in shower, because tiles and grout are not a waterproof layer and never were. Our bathroom installations page sets out what a full refit involves.