I have two different inflatable mattresses (NOT self-inflators - you need to blow them up yourself).
I have a 'hikers' mattress, that I got from Argos a few years ago. It looks EXACTLY like the Blacks hikers mattress. These are the ones with several individually inflating tubes, like a beach lilo. They take only a couple of good puffs to inflate. They roll down to a nice small size - about the same as a kitchen roll.
I also have a traditional inflatable blue-flock camping mattress that I got from Tesco ages ago for a fiver or so. This takes about 15minutes to inflate. But it is VERY comfy.
I'm a real fidget in bed, and get really uncomfortable. For that reason, I nearly always take the Tesco camping mattress - it's big and bulky but I get a good sleep. But if you're not so fussy then the hiker's style will be much better because it's smaller, lighter and quicker to inflate. I would emphasise that I am REALLY fussy, so don't be put off by my preference.