Comparable softness/support

We currently have a millbrook plc 2000 mattress and sprung divan in superkingsize. It is categorised as 'firm' support but actually feels quite soft yet very supportive.We are looking to replace it and wondered which sort of artisan mattress you would suggest. Also, would you let me know what is the difference between pocket sprung and bonnel coil?Finally, how does the mattress which you suggest for me compare to the Millbrook enchantment 3000 please?