I am sorry it has taken a while to get to you.
I must advise you, that you must go through the local Council Planning Office with this. I am afraid that they will need detailed drawings showing load bearing measurments drawn up by a professional. It isnt something that an amature should get involved in. ( sorry I do not mean to demasen you) Also with professional advice they would have Personal Indemnity Insurance. If you are using a builder He should get this for you. before any work takes place.
I hope that this helps you