On the subject of what to wear inside a sleeping bag, I have found that cheap thermals make good PJs. They are light, trap the air to make a warm layer next to the skin and are stretchy and comfy. And the issue of having less air inside the selling bag, I bought myself a Selk bag years ago, a sleeping bag with arms and legs, so it is snug but places no restrictions on movements. I may look like a giant jelly baby, but that is a price I am prepared to pay!
Thank you everyone for your helpful comments. I took them all onboard and did a combination of things:
1. Used a footprint for first time
2. Used SIM under inflatable bed
3. Blanket on top of air bed
4. Hot water bottle to warm sleeping before getting (removed once in)
5. Wore only a nightshirt
Result? Completely toasty
Actually were the 2 best nights sleep ever in tent and totally sober!!
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.