I hate being wrapped up when camping, so we take an oil radiator 1kw heats a five man tent lovely (safe to leave on all the time). I take a double outwell campbed and just a 5cm sim and I put an electric blanket on the bed to warm it up and then unplug for the night. The campbed has the advantage of loads of space underneath for tubs of clothes etc.,
We are always warm as the heat is consistent, and the condensation minimal.
If you dont want to take an elec blanket, then a couple of hot water bottle do the same job but not as toasty. We also put a duvet INSIDE our sleep bag if its really really cold.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.