Yep, sure about the doors and alarms.
Does the building inspector not need to come and sign off your new conservatory?
Also, when you sell the house it could be an issue if the buyer has a good solicitor.
I went to see a house once where the original doors were in the shed and the cheapest of the cheapest of fire doors were in place in order than they could sell it (house had a loft extension) - but they made no secret of the fact that you would just swap the nice doors back on once the sale went through.
EDIT: isn't the permitted development for a conservatory 3m, not 4m?
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