Comparison before we buy?

I have just discovered you and wish I had more money! Myself and partner currently have a slatted bed base and memory foam mattress which is creating issues for us, I have had a stiff neck for the last 6 months, I also get a stiff lower back after laying too long. We are both around 5' 4" and weigh around 10 stone each. Your entry level says soft but should feel medium to us but is there any other bed we could try as a comparison before we buy as we are both concerned it could be too soft for us? We live in London Brixton.