Bathrooms in Solihull are more often about adding one than replacing one, because the houses have the space and the layouts frequently have somewhere sensible to put it.
Adding an en suite or a second bathroom raises three questions in order. Where does the waste go, because a new run needs a route to an existing stack with adequate fall and it cannot cross a room at ceiling level without somebody noticing. What is the floor doing, because joists sized for a bedroom are carrying a filled bath on a tiled floor, and on the longer spans in these houses that needs checking rather than assuming. And what does it do to the room it comes out of, because a bedroom reduced below a sensible size to gain an en suite is not always a good trade.
Where the property is in the affected part of Olton, any external work that goes with it, a new soil pipe on an elevation or an extractor outlet, may itself require permission under the Article 4 direction.
Ventilation matters and gets treated as an afterthought. An extractor discharging into a roof void puts the moisture straight back into the building.
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.