Which mattress with back, knee and hip problems.

My husband and I recently arrived in UK from South Africa. We sold our bed there and need help in choosing a new one. I am 145kilograms my husband is 92 kilograms, he has serious neck problems and I have a ruptured and now disintegrated disc on my lower back and arthritis in the knees. We used a Henwood pocket spring with memory foam there as I need support to take the weight of my hips and shoulders and for my lower back. If the net tress is hard, which is what we wre on at our current rented apartment it causes pain on waking in my back, shoulders and elbow. I react badly to chemical products and like your calico pocket springs and natural fibers. Our previous bed was covered in a lovely bamboo material. I need good edging support due to me weight. My husband is fine with having the same springs as me. In SA we had what we call an extra length King size bed. Sizes in UK seem to be different to those in SA. Our bed was 180cm x 200cm. What size is closest to that? I am 5\'10\" and my husband is an inch taller. We are looking for a home now and will need a bed when we find one, hopefully by the end of August. Which bed do you recommend? How long would it be to have it ready for delivery? I like a luxury soft feel but with excellent support. Please give us your advice.