This deal from Wowcher
From £89 for a Coolsleep memory foam layer mattress in small single to king sizes from Desire Beds!
Cooling mattress: Get comfy with a two inch layer of Cooling Marble Memory Foam. Memory foam layer: Moulds to the shape of your body and relieves pressure points. All foam: Plus a firmer six inch layer of orthopaedic Reflex Semi-orthopaedic foam. Medium firmness: With an approximate depth of 21cm, it provides overall support for your whole body. Hypoallergenic: Antibacterial with hypoallergenic filling to prevent dust mites. Sizes: Small Single, Single, Small Double, Double and King.