Best single mattress recommendations?

[beonmywaythen]

We're buying a new single mattress for my DS. I want it to be good quality but also don't want to overpay. Any recommendations on good mattresses that last?

Anyone?

Ikea Malfors firm or medium. Around £100 and so far lasted our DC perfectly for more than 3 years, expecting at least another 3 years out of them.