Coolflex� King-Size Mattresses

By Jason · Updated 9 May 2026

Coolflex is a UK mattress brand built around one idea: stop the bed running hot. The range covers hybrid, pocket sprung and memory foam, all priced at the affordable end of the market and sold direct through MattressNextDay. We list around 750 across all sizes, from singles for spare rooms to super king for the master.

What Coolflex actually do

Coolflex makes value-priced mattresses with a cooling angle baked in. The brand's pitch is that mattresses don't have to feel hot or claggy after a few hours, and the engineering aims at airflow, breathable covers and gel-infused fills wherever they fit the price point.

The lineup is mattresses-first. Coolflex doesn't make headboards, bases or bedding. The mattresses come in three constructions (hybrid, pocket sprung and memory foam), at standard UK sizes from single to super king. Most sit between £150 and £400 depending on size and depth, which is meaningfully under the established names like Silentnight or Sealy. Coolflex isn't claiming to outclass a £900 Hypnos pocket sprung; it's a budget-with-tech alternative for buyers who'd otherwise look at IKEA or Dunelm mattresses.

The lineup explained

Pick by construction, then by size. Each construction handles weight and movement differently.

The Coolflex Hybrid range is the volume seller. Pocket springs underneath for support, foam comfort layers on top with cooling-gel insertions. Suits couples and side sleepers, especially anyone who finds straight memory foam runs hot. Most Coolflex hybrid models sit between £200 and £400 depending on size; king and super-king sizes go higher.

The Coolflex Pocket Sprung is the more traditional construction, with independent springs in fabric pockets and light foam layers on top. Pocket sprung is what you want if you and your partner sleep at very different weights, because the springs respond independently and movement doesn't cross the bed. Coolflex's pocket sprung options are firm-leaning rather than plush; the price points sit slightly under the hybrid line.

The Coolflex Memory Foam range is all-foam construction with cooling-gel layers. Best for solo sleepers, or anyone with specific pressure-point pain who wants the contouring memory foam gives. It's the construction that runs hottest by default in any brand, so the cooling tech matters most here. If memory foam appeals but you've been put off by the "sleeping on a hot waffle" reputation, this is where Coolflex justifies its name.

For sizing, the Coolflex King Mattresses and super-king options are the most-bought across all three constructions. Singles and small doubles are common spare-room buys.

Cooling tech, plainly

Cooling-mattress claims are easy to oversell. Here's what Coolflex actually mean by them: gel-infused foam and breathable covers slow the rate at which body heat builds up under the duvet. They don't refrigerate you. They don't turn a 25°C bedroom into 16°C. What they do is shift you from "had to throw the duvet off at 2am again" to "got through the night under it".

That's not theoretical. I run hot in bed. Half the year, UK summer plus the warm spring and autumn nights either side of it, my own bed gets too hot to sleep under a duvet, so I ditch the duvet entirely and sleep under just a sheet. A genuinely cooler mattress, hybrid or gel-infused pocket sprung, would push the line at which that switch happens. That's the realistic outcome to expect, not Arctic-grade thermal magic.

How to choose

Construction first, size second, budget third. If you're a single sleeper or want maximum contouring, look at the memory foam range. Couples sharing a bed at very different weights, pocket sprung. Anyone wanting a balance, or anyone who's been burned by an all-foam mattress running hot, hybrid is the safe pick.

For sizing, allow at least 2.7m total bed length plus 30cm clearance round the bed; super-king (180cm wide) only fits properly in master bedrooms. For spare rooms, single or small double rather than oversized.

Where to buy

Coolflex mattresses are sold exclusively through MattressNextDay. There's no John Lewis or Dunelm stocking them; single-retailer brand by design. MattressNextDay's standard delivery is one working day to most UK postcodes, free over £40 (which every Coolflex mattress is), with a 100-night trial and a 10-year guarantee on the springs. Returns within the trial window are free; outside it, return shipping comes off the refund.

Frequently asked questions

Are Coolflex mattresses any good?

For the price, yes. They're not premium-tier; comparing a £250 Coolflex Hybrid to a £900 Hypnos isn't a fair fight. But for budget-with-tech where cooling matters, Coolflex sits clearly above generic budget mattresses you'd find at the supermarket end of the market.

Where can I buy a Coolflex mattress?

MattressNextDay is the sole UK retailer for Coolflex. The brand isn't stocked at John Lewis, Dunelm, IKEA or any of the big high-street names. Buy direct via MNd or you won't find it; that's the trade-off Coolflex makes for its lower price point.

What sizes do Coolflex mattresses come in?

All UK sizes: single (90cm), small double (120cm), double (135cm), king (150cm) and super-king (180cm). EU sizes aren't part of the standard range. Depth varies by model from around 18cm up to 28cm; deeper isn't automatically better, just plumper.

What's the difference between Coolflex Hybrid and Pocket Sprung?

Hybrid combines pocket springs with foam comfort layers and cooling gel; pocket sprung is springs alone with light foam toppers. Hybrid suits couples and side sleepers; pocket sprung suits couples sleeping at very different weights, because spring-only construction handles weight transfer better than foam.

Do Coolflex mattresses really sleep cooler?

Yes, but realistically. Gel-infused foam slows heat build-up; it doesn't refrigerate. If your current mattress wakes you up at 2am with the duvet thrown off, a Coolflex hybrid or gel pocket sprung will likely push that further into the night or remove it entirely. It won't make your bedroom cold; that's down to the room.

Is there a Coolflex warranty and returns policy?

10-year guarantee on the springs (industry standard), and via MattressNextDay a 100-night trial. Free returns within the trial window. The mattresses must be unsoiled and in their original packaging or fitted with a mattress protector to qualify; standard manufacturer terms.