Help selecting a mattress

Hello
We would love some help selecting a new mattress. Until recently we have had a Myers 'Marlow' mypaedic mattress with the following spec: 325 springs in every 150cm super strong springs, myerpaedic deep fill. My husband always slept well in it, as did I although I found it quite hard on the shoulders and found they would pop a lot during the night. However, since the mattress degraded my husband started to suffer with lower back pain and we have been trying to find the right mattress.
We have just tried a Leesa mattress for the last 60 nights which has been unsuccessful, we do not like the sinking feeling and my husbands back pain has got worse. Last night he slept in another bed with a firm mattress and also found his back pain was bad.
We think a pocketsprung would be best for us, we both get hot in the night and use a summer duvet all year round. We want a mattress that supports my husbands back but is comfortable and is gentle on the hips and shoulders but without sinking in. I am 5"7 and 13 stone, my husband is 6"2 and 14 stone. We're happy to look at the best mattress for our needs.
Thank you!