Dormer extension

Hi,
I am thinking of getting an extension in my Dormer Bungalow in the up stairs at the back. This will entail two attic like windows to the back. The house is a semi and the extension will overlook my neighbours backyard which is already slight overlooked.

a) Do I need planning permission for this?

b) How do I go about getting this done. Do I need an architect?

c) In this extension I would like to put a family bathroom and a bedroom. The Gas boiler and Water tank are on the space the bathroom would be. Would one or both need to be moved?

d) Could someone be able to give a rough ball park on how much this might cost? (I wont be doing much of the work myself. I know this is difficult but just a guess will do)

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Also I would like to knock the Bathroom on the group floor and add the space the living room. Then add a guest W.C. under the stairs. The ground flood has wooden beam flooring so I guess plumbing could be do under that.
e) How much extra would that cost? Are my plumbing assumptions correct?


Kind regards, Kevin