Sleepeezee ActivFlex Response 3600 Memory Mattress
The Sleepeezee ActivFlex Response 3600 is a soft memory mattress that pairs 3600 pocket springs with foam and cooling gel layers.
- Soft feel with real spring support
- Cooling gel in two layers
- Made in the UK, vegan-friendly
£799
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The Sleepeezee ActivFlex Response 3600 comes in UK Single through to Super King. At 33cm deep with a pillow top built in, it sits firmly at the plush, hotel-style end of the spectrum. Sleepeezee is an NBF-approved manufacturer, the mattress is made in the UK, and it carries a 10-year manufacturer guarantee. It suits sleepers who want a soft, cushioned feel with proper spring support underneath, although anyone after a firmer surface should look elsewhere in the range.
Mattress specifications
Firmness
Soft
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)
Side Sleeping
Certifications
BS 7177
Assessed from the specification published by MattressNextDay, captured September 2026, and from regular price comparison across our UK retail partners.
Why should you choose this mattress?
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 in larger sizes, but the 10-year guarantee and 33cm build offer some reassurance for the outlay.
Key features & layer details
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.
Best suited for?
Side sleepers
The soft pillow top and ActivFlex spring foam layer contour to your shoulders and hips, giving cushioning where side sleeping puts the most pressure.
Warm sleepers
Staycool gel in both the pillow top and a dedicated layer draws heat away and manages moisture, so memory foam is less likely to leave you hot.
Allergy sufferers
The mattress is described as hypoallergenic, which makes it a sensible pick if you want bedding that suits sensitive sleepers.
Lighter sleepers
A soft, plush feel and a pillow top with mini comfort springs give a cushioned surface that lighter bodies can sink into comfortably.
Eco-conscious buyers
It is vegan friendly and made in the UK by an NBF-approved manufacturer, which suits anyone weighing up where and how their mattress is made.
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 if you prefer a firm feel, this might not be the best choice.
Save on an earlier or ex-display model
Some retailers still sell the earlier version of this mattress, or ex-display and returned stock at a lower price. These are the sizes where it costs less than the current model's best price.
Sleepeezee ActivFlex Response 3600 Memory Mattress
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FAQ's
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 paid 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. Every size is 33cm deep, so check your fitted sheets will stretch to a deeper mattress.
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