Your conservatory had time to get cold by radiation into the night sky before the warm front moved in so it was able to condense the water vapour. My oen porch is the same under these conditions. Also affected by the time at which you turned off the heating in the conservatory if you were so irresponsible vis-a-vis global warming to actually turn it on in there at this time of year. Heating conservatories should be illegal by now, far more wasteful even than petrol cars.

Condensation in the presence of a damp warm front and change in temperature will have made hundreds of garages and equivalent unsealed barns etc damp. This illustrates the problem for people who think it is clever to have vents in their workshop to "let the cold air out". Rubbish. It let the damp air in, Always strive to make your workshop airtight so the condensation stays on the outside of the walls and windows.

If the conservatory is modern, do you have modern self cleaning glass – if so, it is prone to fogging as you experience.

We had new windows a year or two back. Previously had wood frames with probably 20 year old sealed DG units, would get condensation on the inside on very cold nights. New windows are modern aluminium with thermal break inside and modern wide gap glazed units. Since then we almost never get internal fogging on the woindows but regularly get condensation on the outside in cold weather.

House I lived in in Dublin was of a simple kind, the temp inside and outside was always the same, FREEZING !

One never had to go outside to check the weather, it came in to you ! An early form of Air Conditioning, I suppose !