Stig, if money is tight you could take duvets and blankets from home instead of forking out for sleeping bags. Just make sure that you put a blanket on top of the airbed if you use one.
we had really good sleeping bags last yr (OH had an argos 1). I was lovely and warm and OH was slightly chilled to say the least. Then we upgraded and are now toasty. We sussed it last October when we went to blackpool and it was chilly - airbed with sheet, then thick blanket, duvet and then the sleeping bags. We took our thermals as well but i had to take em off in the middle of the night because it was that warm. We did this when we went away at the end of October for Halloween and were really toasty. a thick blanket on top of ur airbed help with the coldness from it - as they do get cold and i think its because when u get on it theres no way of warming it up so u and the airbed stay cold. Leave the sleeping bags and use the duvets and blankets for the time being - after all u have them anyway. Dont forget ur jumpers at the side of the bed also just in case
millets have some sleeping bags half price for £7 and junior ones for £4 if this is any good also i have the 400grm envelopre bag from argos and it has never let me down yet.
I bought the 400 gsm ones from Argos yesterday. The cowl ones for us and the straight topped one for daughter. £199.99 and £14.99. They seem nice and thick and warm. In fact, OH and Daughter slept in theirs last night and ended up out of them underneath.
I tried to explain they are meant for March camping not centrally heated house!!
------------- "Everywhere you go, you always take the weather with you!"