Firmness
Type
Memory Foam
Depth (cm)
33
Number of Layers
6
Trial Period (nights)
Warranty (years)
10
Price Range
£799 to £1,549
Best Sleeping Position(s)
Certifications
Assessed from the specification published by MattressNextDay, captured September 2026, and from regular price comparison across our UK retail partners.
The main draw here is the combination of memory foam comfort with genuine spring support. The ActivFlex spring foam layer is designed to mimic how pocket springs respond while moulding like a foam, which means you get contouring without the sunk-in feel memory foam is sometimes known for. Cooling is taken seriously too: Staycool gel appears in both the pillow top and a dedicated layer, drawing heat away and managing moisture, useful if memory foam has left you warm in the past. It's hypoallergenic, vegan friendly and made in the UK by an NBF-approved manufacturer. The price climbs towards £1,549 in larger sizes, but the 10-year guarantee and 33cm build offer some reassurance for the outlay.
Key Features & what's inside
- Soft Knitted Cover. A highly breathable knitted cover that's soft to the touch. It gives the mattress a genuinely plush finish.
- Pillow Top with Mini Comfort Springs and Staycool Gel. An additional pillow layer containing up to 1000 mini comfort springs plus Staycool gel, which means the surface actively draws heat away from your body while you sleep. This is where much of the soft, cushioned first impression comes from.
- Soft Polyester Comfort Layers. Soft polyester layers that add full-body cushioning. They soften the transition between the pillow top and the layers below.
- ActivFlex Spring Foam. An innovative layer designed to mimic the precise support and movement of pocket springs while moulding to your body like a foam. In practice, that means contouring without feeling stuck in one position.
- Staycool Gel Layer. A dedicated gel layer that manages moisture within the mattress and aids temperature regulation. A sensible inclusion, since foam layers can otherwise trap warmth.
- Pocket Springs and Mini Comfort Springs Core. The core combines full-size traditional pocket springs with mini comfort springs, 3600 pocket springs in total. This gives targeted support to key areas of your body, so heavier zones like hips get more push-back.
Layer details from mattressnextday.co.uk product page, September 2026.
Who's it NOT for?
This is a soft mattress, so it's a poor match if you prefer a firm surface or you're a heavier back or front sleeper who needs more resistance. The built-in pillow top can't be flipped for a different feel. Hot sleepers wary of memory foam should be reassured by the gel layers, but committed firm-feel fans should look elsewhere.
Sleepeezee ActivFlex Response 3600 Memory Mattress
Is the Sleepeezee ActivFlex Response 3600 soft or firm?
It's a soft mattress. Between the pillow top, polyester comfort layers and memory foam, it delivers a plush, cushioned feel, while the 3600 pocket springs underneath keep the support consistent. Lightweight sleepers and side sleepers tend to get along best with this kind of tension.
How many springs does the ActivFlex Response 3600 have?
The core contains 3600 full-size pocket springs alongside mini comfort springs, and the pillow top adds up to 1000 mini comfort springs of its own. Pocket springs move independently, which means less motion transfer if you share a bed.
Does the Sleepeezee ActivFlex Response 3600 sleep hot?
It's built to counter that. Staycool gel features in the pillow top and in a separate layer that manages moisture and helps regulate temperature, and the knitted cover is highly breathable. If memory foam has felt warm to you before, this design directly addresses it.
What guarantee does the Sleepeezee ActivFlex Response 3600 come with?
It carries a 10-year Sleepeezee manufacturer guarantee, as stated on the MattressNextDay listing. Note that delivery terms are the retailer's own: MattressNextDay lists free next day delivery to almost everywhere in mainland UK, with some addresses incurring a small fee, and old mattress removal as a £39 add-on.
What sizes does the Sleepeezee ActivFlex Response 3600 come in?
It's available in UK Single, Small Double, Double, King and Super King, priced from £799 to £1,549 depending on size. Every size is 33cm deep, so check your fitted sheets will stretch to a deeper mattress.
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