A nice, big soft zip and link bed for a hot climate!

I am a post menopausal Brit living in Southern Spain. Therefore the challenges of choosing a new bed/mattress are many. I am 81/2 st, husband just over 11st wet. I get hot all the time, summer here in the 40'sC. We both think we like something softish to lie on, definitely not 'orthopaedic', but we also have bad backs. Both at the Osteopath currently... We currently have a 5ft Vi-spring which has a permanent hump in the middle because husband does not want a hernia turning mattress over. What we want is a 6 - 6.6 zip and link for ease of turning but need advice on what sort and you guys seem to be the ones to ask.