The bathroom has been replaced with a room containing a bath or shower, this is to allow for when a shower is fitted in a bedroom, the sink does not matter, it is distance from bath or shower, which needs to be over 3 meters, which in real terms replaced the rules for fitting a shower in a bedroom as 3 meter plus long bathrooms are not very common.
Problem is moving a bathroom is notifiable work, so you need to satisfy the LABC inspector. And this is the problem, it may seem to tick all the safety boxes, but it depends what he will allow.
I had a problem with late parents house. We had a builder in to do the work, and assumed the builder was doing everything by the book, he walked off the job, so son and I took over, so step one was tell the LABC we were taking over the job. Seems the builder had not told them, had I known I would have likely also not told them, mainly as I didn't know planning permission was required to move a bathroom or kitchen. And the inspector arrived with his wagging finger why had we started without getting permission.
He insisted on an extractor fan even with opening windows, and this is your problem, if he says no, it is no.
So it seems you need to submit detailed plans, it helps you, if detailed and it shows extractors, washing machine, FCU etc. Then they can say no before you start, to fit the ceiling then find I needed a duct and extractor was not funny. So you have paid £100 plus vat for the planning permission so get the inspector to tell you what is permitted.
Also there is the Part P thing, both bathroom and kitchen are special locations, I note Monmouthshire is in Wales. So again down to what the LABC inspector will allow you to do? I had a problem getting the inspector to allow me to do my own inspection and testing, we had the meters on view when he arrived, so clear we could test and inspect, and both my son and I had our city & guilds 2391 which is the exam to show you know how to inspect and test, only when my son said anyone inspecting our work would need to be higher qualified than ourselves and my dad has a degree, did the LABC inspector say we could do our own inspecting and testing.
And after all that, the LABC inspector missed that the lintel over the door was only supported on one side.
After all the problems with wet room, when it came to a full re-wire I employed a scheme member electrician to rewire the house, so LABC not involved.
You must remember our English cousins put in a load of rules, then gave Wales its own control, then removed the rules for England, but not for Wales, so our English cousins are often unaware of the Welsh rules even when they made them to start with. I find it a problem with tradesmen from England, they often don't realise either they are working in Wales or the rules are not the same.
Cymru am Byth
As an after thought, is BS 7671 valid in Wales? All rules and regulations in Wales need to be published in English and Welsh, I don't think BS 7671 is published in Welsh, so likely not valid, also of course any rule which refers to BS 7671?