Deciding on the best mattress and base for us

We are looking to replace our whole base and mattress. We currently have a memory foam mattress on a slatted wooden base which has been comfy, but the mattress probably over 10 years old. Although it still seems comfortable I suffer from allergies and feel that we could probably do with a fresh mattress. We are after a king size bed and mattress. I'm about 9.5 stone and my husband is about 12.5 stone. We are looking for a medium firmness and would like to get a divan base with 4 drawers. We could spend about £1000 in total. Although you're website is very comprehensive I've still got a bit boggled at where to start. So I would be grateful if you could give me some advice on which mattress to chose.