My current mattress came from Argos, out of desperation to replace the hand made one I had before. The rest of the bed I made, and will be making another one when the bedroom is done.
My folks have a habit of getting ex hotel beds, from a local secondhand furniture place, for my guest rooms. I'm not really keen on them as I don't know how clean or worn out they were before the new fabric was 'stuck' over the tops of the mattresses.