I want to order a king size mattress for my parents who live in rural Scotland; I live in France so I can't really help a lot with putting it in. They have been sleeping on the same foam mattress since before I was born and I am 32. I changed their sheets when I was visiting last weekend and basically the only thing holding it together is the mattress cover. I would like for them to have a comfortable firmish not-too-thick mattress, to replace what they have, but I don't think it needs to be massively high tech because at this point I am convinced anything would be an improvement. But there seems to be an endless amount of choice and I don't know if there are some I should absolutely avoid or what the gold standard in mattresses would be.
They are not really up to lugging such things upstairs, so I am also looking for recommendations of companies that will deliver and put it in place, and also with any luck take the old one away, if anyone has any ideas.