My husband and I need different firmness of bed due to back problems. I see a lot of information about zip and link beds, but when looking to purchase they all seem to be sold by the pair. Is there any company that does 'mix and match' zip and link so we can buy one half firmer than the other?

My husband and I both have back problems. We bought a Rest Assured Bedstead 1400 Ortho about 3 years ago when we first moved in together. For a while it was fine, and my husband still loves it. It didnt stop the back pain for either of us but certainly was better than our previous beds. I started to get to the point where pain was seriously impinging my sleep and this would abate within a short time of getting up. I added a think memory foam topper which helped for a while. I am hyper-mobile throughout my body. I went away for a week and found my back much better, due to increased space and no tossing and turning from himself moving my side of the bed around. We are lucky to have a camper van, so currently I am sleeping on our double memory foam roll cheapie mattress from mattressman and he is on the Ortho1500. Its much much better for my upper back, but my lower lumbar/pelvis is starting to have issues.. it feels as if my ample bottom is sinking further than it should so I’m folding upwards into a banana shape, where with the firmer Ortho1500 my upper spine flattens into it when on my back needing osteopathic help to realign it on a regular basis, and on my side my whole body becomes twisted, but it supports my lower back well when lying on my back. (with my condition, my body will mold to whatever position its put into rather too well!). We have tried both sleeping on the memory foam but I again slept really bad due to lack of space to stretch and move during the night. We are considering practical long term solutions, especially as we’re only a year married!) and think that two singles or a zip and link may suit, especially given the extra width. We dont have a huge budget and would prefer to spend as little as possible, but we’ll find the money somehow if needs be as it affects our quality of life so much. I am 5ft 6 and weight around 11stone, my husband is 5ft9 and weights around 15stone. Any help or advice very gratefully recieved. >