Hello and welcome to the site Leese.
Thanks for all the comments and advice so far. I'm pretty much sold on a srung not foam mattress.
Bee, like some of the others on the thread, my experience of futons has been that they are pretty uncomfortable. The rolling up theory may work for comfort but, would defeat the object for us as we want a sofa to sit on when it's not being used as a bed for guests.
SueDonim, what is a jaybee click-clack sofabed? is there somewhere that I can find out about these things?! I feel a bit silly for not knowing.
Leese, I had seen adverts for the sofas-direct type service but didn't know about the quality, so it is good to hear from someone who has actually bought one of their sofabeds.
Berries and cos, I thought all the ikea sofabeds were foam matressees, do either of you know if the have spring mattresses?
I will try and find out about the sofa and sofa bed store - hopefullt from the internet as shopping time is severely limited due to the fact that dh and I are both working full time AND we both hate shopping...
SueW, I don't suppose you remember where you bought that lovely sofabed all those years ago, do you?
Once again, thanks for the info given so far, I'll start investigating tomorrow.