I have just come back from a weekend tour in the North of the Netherlands. It was cold: the coldest September night since 1971, with temperatures just below freezing. Riding during the day was fine, with some sunshine, though also with headwinds for much of the Saturday. I stayed at a campsite in a National Forest. Facilities were basic but included warm showers, and that is enough for me. I managed to cook dinner before dusk (at about eight), and after that could join a group of fellow campers who had started a fire in the fire pit. I went to bed at ten when it was getting too cold to sit around.
The night was cold, even though I had brought an Exped down mat and a warm winter sleeping bag that should be fine for rather colder temperatures. In the middle of the night I woke up and decided to also put on my down vest, which helped quite a bit. The reason I was feeling cold was simple: I had taken my son's festival tent, a Decathlon Quickhiker 2. I had used this before and had been quite happy. What I had not realized was that it has large mesh panels that you cannot cover, unlike on our larger Hilleberg and Helsport tents. Also, the flysheet does not quite reach to the ground in some places. In short, a great tent for summer in France, but not in the cold. So my lesson would be to avoid such tents (and that includes many US style inner first tents) if you want to camp in colder weather.
The morning presented another typical winter camping problem when I got up at eight: the long grass was very wet, so my Goretex shoes got pretty wet as well, though not my feet. But wet shoes are cold (even more so once on the bike). I left at 9.30. The first hour was still a bit cold, and I had to wear my down vest under my Goretex jacket, and a buff under my helmet, but soon enough I could take off much of the warm clothing. Unlike on the Saturday, it was and remained too cold for bare legs. When I arrived home, the first thing I did was dry the wet tent.
For my next trip I will try to find a camp site with a restaurant to spend the evening. I wil also try to persuade my wife to come along so we can take the Hilleberg and keep it warm. For the one after that I will probably book a hotel. I have added a proper cold weather solo tent to my wish list. Current favourite is the Helsport Ringstind 2.