Replacement for Mirroform mattress

We have a very old Mirrorform mattress (Super King size) which we are looking to replace. It offers little support now.
We've already been in touch with you about modifying the divan base (remove slats and replace with solid and supported ply) which we will be doing.
We're now looking at your Artisan Natural Zip link Super King size and trying to compare it with the alternative John Lewis John Lewis Natural Collection 6000 Egyptian Cotton springs/" title="pocket spring">pocket spring (£1600). Do you have any guidance which might help in making this comparison?