Also, to the OP, your architect did not put in the loft plans along with the application for the side and rear extensions because it sounds like they were put in under an actual planning permission and your loft design would NEVER be approved under planning.
However, your loft plans DO seem to be LAWFUL under your permitted development rights.
The only way to be 100% certain, and be able to give 100% certainty to anyone who has inclination to ask (which could include the council themselves) is to apply for a certificate of lawful development.
You should be aware that you can apply for this before OR after you have finished work. BUT, if you have already started (or completed) the works then the cost for this application is DOUBLE.
Considering that any number of people could ask for proof that your dormer is lawful, and that it costs less to do this before the fact, I'd always recommend just submitting to the planning department for a certificate of lawful development... You've even already had the drawings put together so its not like you need to pay to have them done... its just hte form filling, so you can do this yourself if your architect wants to charge too much for him to deal with it on your behalf.
However, your loft plans DO seem to be LAWFUL under your permitted development rights.
The only way to be 100% certain, and be able to give 100% certainty to anyone who has inclination to ask (which could include the council themselves) is to apply for a certificate of lawful development.
You should be aware that you can apply for this before OR after you have finished work. BUT, if you have already started (or completed) the works then the cost for this application is DOUBLE.
Considering that any number of people could ask for proof that your dormer is lawful, and that it costs less to do this before the fact, I'd always recommend just submitting to the planning department for a certificate of lawful development... You've even already had the drawings put together so its not like you need to pay to have them done... its just hte form filling, so you can do this yourself if your architect wants to charge too much for him to deal with it on your behalf.