We camped in wales last weekend also no ehu, it was cold but we were fine, I had a sleepiungbag, liner, extra blankets , dh had a duvet and also extra blankets.
I think synthetic fibres are not good, they get me so overheated I get all sweaty and then cold. So we got layers of natural fibres like a wool duvet,cotton throw x2, cotton bedspread and silk and cotton throw.
I cant sleep in a bag, just keep getting tangled and trapped. They are the best thing for keeping warm though, well the good ones are. We use a couple of fleece blankets on top of the airbed, kept secured by a fleece topped fitted sheet. We then sleep under an opened out bag and have a couple of fleece blankets on standby. We never use EHU and get no condensation, if it get's a bit cold I wear a long sleeve T shirt and have a thinsulate hat (which I've never worn)