I tested the M&S 'Stay Cool' mattress topper during a heatwave – as a hot sleeper, here's what I thought of the £75 cooling buy

I put the M&S Stay Cool 10cm Depth Mattress Topper to the test to see how it compares to the best cooling mattress toppers on the market.

In a nutshell

As a sleep-product reviewer, I’ve tested some of the best mattress toppers out there, including two of my favourites for hot weather or hot sleepers: the Woolroom Deluxe Wool Mattress Topper and the Simba Cool Foam mattress topper.

So when I heard about Marks & Spencer’s latest cooling mattress topper – the relatively inexpensive M&S Stay Cool Mattress Topper, which is £75 for a single – I was keen to give it a test run.

Overall, I was fairly impressed. This topper doesn't offer much support, but if you like a soft, sink-in sleep surface, I found its 10cm deep polyester fill was comfortable.

I’m also a fairly hot sleeper, who, like Goldilocks, struggles to sleep unless my temperature is “just right”, and whilst I didn't find this topper actively cool, it also didn't make me overheat (even when testing it during a heatwave).

The main downsides (for me) are the fact it can't be washed, needs regular shaking to 'refluff' it, and I do prefer a bit of a more supportive sleep surface.

However, the M&S Stay Cool is good value for money, and, whilst some toppers do offer better cooling relief for hot sleepers (more on those below), if you're looking for a soft topper that can provide a 'breaker' layer between a sweat-inducing mattress and your body, it does the trick without breaking the bank.

Specifications

• RRP: £75 / £85 / £95 / £105
• Sizes: single / double / king / super-king
• Depth: 10cm
• Construction: polyester cover, polyester wadding fill
• Care instructions: do not wash, do not tumble dry, do not dry clean
• Manufacturer sleep trial: no

Attaching the topper to the bed

The M&S Stay Cool mattress topper comes in a large fabric carry case. This might be handy if you need to pack it away often – if it’s for a sofa bed or a campervan, for example. The bag is definitely designed to be reused, with reasonably strong zips and reinforced edges.

The mattress topper itself was folded inside the bag, and was easy to pull out and slide onto my bed. There was no off-gassing smell or waiting for it to replump like you get with memory-foam mattress toppers.

When it comes to attaching it to your bed, there are thick elasticated straps at each corner. This easily slid over even my very thick Brook + Wilde mattress.

There is no anti-slip coating on the bottom of this topper, but this didn’t seem to matter as it stayed in place well.

Comfort

I took the Simba Cool Foam topper off my bed to test the M&S Stay Cool topper. The Cool Foam is a medium-feel topper, and the M&S Stay Cool is noticeably softer still. This topper is definitely designed to soften a mattress rather than to boost support.

This stacks up when you look at what the fillings are in the M&S Stay Cool topper. It’s made from 100 per cent polyester. This tends to be much squishier than fillings such as memory foam and the micro springs you find in hybrid mattress toppers.

I found that when I lay on it, it gave an immediate feeling of comfort – like being wrapped in a duvet. However, it lacks much responsiveness. Responsiveness is the term sleep experts use when we’re talking about how a sleep surface bounces back and how easy it therefore is to move on your mattress.

If you’re a combination sleeper – ie. you move from back to side to front while you’re sleeping – you’ll appreciate a more responsive sleep surface.

I am a combination sleeper (side and back, if you’re wondering), and found that moving around was fine for me but it wasn’t as smooth as it is on a spring mattress/mattress topper. If you have mobility issues, its sink-in softness may mean it's not the topper for you.

During testing, I used the Stay Cool mattress topper on an already very comfortable mattress so I wasn’t using the topper to improve the feel of my sleep surface.

However, I do think it would work brilliantly to soften up a too-firm mattress, or add an extra layer of gentle comfort. It would be ideal to give a bit of cushioning to those dreaded university student mattresses for example, or to offer a little extra “ahhh” feeling to a mattress or sofa bed in a spare room.

Temperature regulation

Because of its 'Stay Cool' name, the temperature regulation on this mattress topper is one of things I was really interested in. Especially seeing as this topper is made of 100% polyester, and synthetic fibres are often prone to *causing* overheating in bed, not preventing it.

However, while there are no active cooling gels, or cooling fibres, in this topper, it is lofty at 10cm. This means that there should be space between the polyester wadding, which potentially allows for good air flow through the topper, removing hot air and replacing it with cooler air under the body.

I tested this mattress topper during an absolutely scorching British heatwave – record-breaking, in fact. I found that I didn’t overheat on the topper, but I wasn’t completely convinced that it was any more cooling than a decent mattress or a natural-fibre mattress topper.

However – and this is important – I didn’t wake up in a sweaty mess on this mattress topper. Did it make me actively feel cool? No, but it didn't make me feel hotter either. And this can't be said of many of the toppers I've tested.

I do wonder if its breathability might be impacted over time as the wadding compresses under my body weight and those 'air pockets' are lost, but I’m a fairly hot sleeper, and as I say, my sleep wasn’t disturbed when I tested the Stay Cool mattress topper.

Overall, I found the Woolroom Deluxe Wool Mattress Topper, Simba Hybrid Mattress Topper, and Simba Cool Foam Mattress Topper cooler to sleep on. But although I found they did a better job of offering relief in hot weather, they are more expensive.

Care instructions

Caring for this mattress topper is, I guess, very simple, in that you can’t really care for it. The care instructions say that you can’t machine wash or dry clean it.

Considering it's made from polyester (which is usually a fabric that can be bunged in the washing machine on a high temperature), I found this quite surprising. The Silentnight Deep Sleep Ultimate 1000 Mattress Topper we recently tested uses very similar materials, and that can be washed at 40C and tumble dried.

However, whilst this might put off some, you could get around the issue by using a good mattress protector over the topper to maintain a clean sleep environment. You might just want to opt for an extra-deep protector as the loft on this topper is quite high.

I also found that after a week of sleeping on the topper, it needed a bit of a shake-out and fluffing when I changed my bed sheets. This wasn’t a big job, but if you have a larger bed, it does require a bit of upper-body strength. It is box-baffle stitched, which helps keep the fillings in place.

Sleep trial

M&S doesn't offer sleep trials on any of its bedding, which, considering competitors such as Simba, Panda, and Woolroom do, I always think is a bit of a shame.

A sleep trial does help you to assess whether a piece of bedding works for your sleep setup before you commit to keeping it, so without a trial available, it does come down to making your best guess about whether the Stay Cool topper is for you.

Value for money

At £75 for a single and £85 for a double, this topper is pretty reasonably priced.

It's certainly a lot cheaper than some of the best cooling mattress toppers we've tested. For instance, the highly breathable Woolroom Deluxe Wool Mattress Topper costs £289.99 for a double, and the cooling graphite-infused Simba Hybrid Mattress Topper costs £349 for a double.

However, I didn't feel the M&S Stay Cool's cooling powers were quite as good as those more expensive options, and, when you compare it to other toppers of a similar construction, it's actually a little expensive.

For instance, the Silentnight Deep Sleep Ultimate 1000 Mattress Topper is also 10cm deep, offers a similar polyester construction, can be machine washed, and the Silentnight Deep Sleep Ultimate 1000 Mattress Topper currently costs £39.99 at Amazon, or it's £59.99 for a double of the Silentnight Deep Sleep Ultimate 1000 Mattress Topper at Argos.

How I tested

Zoë Phillimore

I’m Zoë, a writer who helps the Ideal Home team put all manner of products through their paces to find the top recommendations for our readers. For this review, I put the M&S Stay Cool 10cm Depth Mattress Topper through Ideal Home's testing process. Here are my sleep stats:

Usual sleep position: side
Tension preference: medium-firm
Sleep problems: hip pain

I tested a king-size version of the Stay Cool mattress topper over the course of a week in a record-breaking British heatwave. During this time I slept on the topper, paying attention to comfort levels and how it affected my sleep. I also pondered how hot I felt sleeping on the topper – this is after all a cooling mattress topper. Lastly, I considered how easy it was to attach to the bed, ease of care, and value for money.