Sleepeezee ActivFlex Response 3600 Memory Mattress
Mattress
Sleepeezee ActivFlex Response 3600 Memory Mattress
Size
Firmness
Construction
Depth (cm)
33
Layers
6
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.
- A plush single for solo adults: Most singles are basic guest-grade options, so a soft pillow top with Staycool gel gives a solo sleeper a genuinely comfortable everyday bed rather than a compromise.
- Compact footprint, full support: At 90cm wide it leaves room for a desk or wardrobe in a small bedroom, while the full pocket spring core still supports an adult properly.
- Cool sleeping for warm rooms: Gel appears in both the pillow top and a dedicated layer, which means heat is drawn away, useful in a small room that warms up quickly.
- A generous guest room option: In a spare room that doubles as an office, this gives visitors a soft, hotel-style night while taking up the least floor space of any adult size.
- Easy bedding to buy: Standard single sheets and a 135 x 200cm duvet fit, and single bedding is the cheapest and most widely stocked of any UK size.
This size suits you if...
You're a solo adult who wants a soft, cushioned mattress in a compact room, you're furnishing a spare room or office that doubles as guest space and want visitors to sleep well, or you're buying for a teenager moving up to a proper adult-quality mattress on a standard single frame.
Consider another size if...
You share the bed regularly, or you simply want more space to stretch out. We'd recommend the UK double instead: it's 45cm wider than the UK single, the same length, and we suggest allowing at least 2.6m x 2.8m of floor space for it.
Similar Mattresses in This Price Range
Did you know? On Mattress Unboxed we have over 1,000 different mattresses to suit all types of sleepers. View all mattresses.
What are the dimensions of the Sleepeezee ActivFlex Response 3600 in a UK single?
The UK single measures 90 x 190cm, or 3ft x 6ft 3in. It's the standard one-person size in the UK, so it fits ordinary single bed frames and standard single bedding without any hunting around. We suggest a room of at least 2.1m x 2.8m to leave walking space around it.
Will the UK single ActivFlex Response 3600 fit a bunk bed or mid sleeper?
Be careful here. The width is right, but at 33cm deep this is a tall mattress, and raised frames usually specify a maximum depth so the safety rail still sits high enough above the surface. Check your frame's stated limit before buying; for many bunks and mid sleepers, this mattress will be too deep.
Is the UK single ActivFlex Response 3600 a good choice for a child?
It can be, with a caveat. It's hypoallergenic and made in the UK by an NBF-approved manufacturer, which reassures. It is a soft mattress though, and a very plush pillow top is a lot of cushioning for a light child. For an older teenager approaching adult weight, the soft feel makes more sense.
How much room does a UK single need in a spare room that's also an office?
Allow at least 2.1m x 2.8m for the mattress with sensible walking space, then factor in your desk. The 90cm width is what makes a single practical here: it leaves wall space free along one side for a desk or shelving, which a UK double in the same room usually wouldn't.
Should I buy the UK single or the UK small double for one person?
If your room allows it, the UK small double gives a solo sleeper noticeably more room to spread out: it's 30cm wider than the UK single and the same length. We suggest at least 2.4m x 2.8m of floor space for the UK small double, against 2.1m x 2.8m for the UK single.