A bathroom is a question of where the water can go, and in Market Harborough the answer is shaped by which elevation the soil stack can appear on.
On the older housing the stack runs externally, and in Little Bowden a new or relocated stack on a front elevation is caught by the Article 4 direction covering front elevation alterations. In the Market Harborough conservation area the same work would be looked at closely as well. Behind the building line there is considerably more freedom, which is where the bathrooms we relocate almost always end up.
Floors are the second constraint. Older 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 causes years of trouble. An extractor discharging into a roof void puts the moisture straight back into the building, and in an older roof it finds the timber.
Tanking is not optional on a walk in shower, because tiles and grout are not a waterproof layer. Our bathroom installations page sets out what a full refit involves.