You say you have just completed the project, if this includes a concrete base this will take probably 1 month per inch of concrete laid so a 4inch thick base would take about 4 months to dry out and you say that you have already sealed the floor so effectively sealing in the moisture this will...
I must disagree with the last couple of posts, modern glazing can give u values that are better than cavity walls ( cavity wall without insulation = 1.9 - celsius one double glazed units = 1.0) ok the target for new build regulations is .35 for cavity walls but thats in a perfect world.
conservatories always used to be fitted with the cheapest sealed units and polycarbonate, but due to customer pressure they can now be fitted with better insulated glass than is used in windows. I'll send you some information if you want which explains it better.
the photo you uploaded shows just chipboard laid on jablite insulation ... are there no joists? if not then this is probably a sign of other bad work. you say that the waste gulley has not been moved and is still under the floor, if this is so then the structure should have had building...
i've been building conservatories for over 20 years and i can say without a doubt that whoever built the foundations dosen't have a clue what they are doing. The top of the footings should be at least 2 courses of brick below ground level to minimise the possibility of frost heave, i would...