Mattress to replace a Silent Miracoil

Wow, what an awesome site. I had no idea there so much went into a mattress (or rather SHOULD go into a mattress!) I am truly enlightened. I've been looking through the mattresses on your site and I am unsure what I should go for. I currently have a spruing slatted bed, and what I thought was a good mattress in a Silentnight Miracoil Memory Chenille, which seems to have just died a death, and has zero side support as it's rounded on the edges with a flat 'non-slip' bottom, which sounded great at the time. Wish i'd seen your site back then!

Anyway, me and the wife are both short and stocky, she's about 12st, i'm 17st (and both going down!), we're looking for a good king size bed that'll be okay on the sprung slatted base we have at the moment (Wife simply hates divans). I initially didn't want to spend any more than £300, but after all this education I see now that is unrealistic, so I'm thinking of around 5-600 quid. What would you recommend from your range?

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