Choice of mattress for wooden bed frame

Please could you suggest a suitable mattress for a wooden frame, king size bed with non sprung slats. My husband and I each weigh between 9 and 10 stone and I sleep on my side. We have previously enjoyed sleeping on a Dunlopillo Sovereign on a sprung slat frame bed. Also, do you recommend placing anything between the mattress and frame? We have preferred latex mattresses to other types in the past.