The stud wall has always been there while Mum has lived in the house so I don't know if it part of the original build or not. The house is approx 50 years old, and the council "did some work" on the bathroom and toilet prior to my Mum moving in so it was probably put in then. One of her friends (old fell in her swimming group, who says he was a building inspector or similar) says she will need planning permission in order to do this as she is reducing the number of rooms in the house! I cannot see this as being correct but thought I would check on here. If it helps this is the only toilet and bathroom in the house.
I will also have to change the lighting a little as the existing bathroom light is on a pull switch, but the toilet light is on a normal switch which will be inside the new bathroom. She wants only one central light and a pull cord putting in the 'toilet side' and the other one removing. I have the capabilities to do this but can I, with this new Part P regulation?