In reply to Chloe:
I'm looking into the same thing currently. Past air beds have been hit and miss from all the usual people (GO,Coleman,Vango). My problem is our tent has a head height of 1.20m so putting a 'deluxe' air bed at 50cm would take up to much room anything above around 20-25cm you start to feel cramped trying to avoid condensation in the morning.
Looking into the self inflating mats Vango have some doubles which seem pretty solid (10cm). I noticed they do a 5cm version which is capable of folding to a single 10cm. Going down to the local independent shop (next weekend) as they seem to have them in stock get a couple out hopefully and get a feel for them.
My thoughts are that since there is a block of foam in there it should resist the compression air beds get over a night. I know my 3/4 self inflating mat does the job, unless that's just psychological due to being under a tarp anything is a luxury.