Mattress would be better for a 76kg man who suffers from hip pain

I am seeking to replace a single size Vispring Supreme Bedstead Medium Mattress which I have perhaps used for too many years which now sags a little in the middle. I now experience more hip pain. As an interim measure at present, I am currently using a Silentnight 1200 Mirapocket medium mattress which feels just marginally too firm - but only marginal. I am 76kg 6ft senior male. I dislike hot beds as they make my legs kick out. The mattress would be on a bedstead with less than 70mm between the slats but I could alter the gap
My search is confined to pocket sprung. Your website leads me to a natural fibre - perhaps the Artisan bespoke 004 or maybe the Artisan Naturals but I would welcome your advice. Selection of the correct type is the governing factor.