Planning permission is solely the decision on what your property is going to look like from the outside.
They do not care what it looks like on the inside and if things are done properly. They decide on the basis of what effect your design will have in the surrounding area. Does it fit in with what else is on the street. Your local council will tell you that it has to be in keeping with the surrounding area and not have an impact on the street view. Sounds simple enough, but really it comes down to the local inspector to rubber stamp it, but generally it is down to whether he likes it or not. If it is the case that he doesn’t like it then he will look at the regulations to see if there is anyway he can refuse. In a lot of cases, I have fought with the local council, that my design is in keeping with other properties surrounding mine. However the answer they give is “just because they have got it, doesn’t mean that you can have it”. where’s the sense in that! Right! It doesn’t make sense.
My advice is … Before you send your application to planning, it is advisable that you call the local council, set up a meeting with a planning officer and show them what you are thinking. This way you will be informed to what parts they would not be happy with and can change them. They also have to write to you outlining what was discussed and the advice they gave you. The leaves you in a good position because you have written proof and the meeting will have to be registered on your application.
However they will charge you £250.00 for this, but in the grand scheme of things, you will be spending thousands on your property and £250.00 is not a lot of money, in relation to them refusing your application and having to wait 8 – 10 weeks.