nice job,think it was a mistake to get rid of the original hall carpet though!
The airbrick should be there to ventilate the inside of the now sealed back room chimney and stop damp forming inside it. Nothing to do with the one in the front room.I didnt put a air brick in the back room, come to think of it I think I should have. Hopefully there will be enough air circulation from the fireplace in the front room...