This £20 M&S cooling sheet is selling out fast – and having tested it ahead of the July heatwave, I can see why

M&S shoppers are raving about this £20 cooling sheet, and with another July heatwave predicted to begin soon, I can see why it's selling out fast.

I slept on the M&S Stay Cool Lyocell Rich Fitted Sheet last night, and I can confirm it definitely feels cooler than any other sheet I've trialed during these past few *very* hot weeks.

When it comes to where to buy bedding to cool down in the heatwave, it seems M&S is the place to shop right now.

Even when the UK *isn't* experiencing extreme temperatures, overheating in bed is a problem many of us struggle with.

That's in no small part due to the petroleum-based polyesters that so much bedding is made from – experts often dub these fibres a hidden sleep thief because they lack breathability and reflect body heat back towards the sleeper rather than letting it dissipate. This causes our body temperature to rise and often wakes us from our slumber.

Manufacturers know how to market to these struggles, so it's little wonder the bedding world is filled with products containing 'cool' and 'ice' in their product names.

However, as Ideal Home's Sleep Editor, I've tested a *lot* of cooling bedding in the past five years, and, unfortunately, I've often been underwhelmed by the claims.

During my team's and my testing of mattresses, duvets, and pillows, we've repeatedly found that, at best, cooling claims can be short-lived cool-to-the-touch surfaces that soon heat up after a few minutes, and, at worst, those claims can be downright misleading.

So when I saw that M&S is selling 'Stay Cool' bedding, I had to admit that despite my faith in the retailer, I was a little cynical at first. But then, I saw the product reviews. Over 600 of them already, and over 400 of those have given this sheet 5 out of 5 stars.

I know that M&S shoppers don't mince their words with their likes and dislikes, so when they say something works, I believe them.

Plus, when reviews sound like: 'It's like slipping into a cool bath without the water,' and, 'These sheets are so cool and comfortable. Highly recommend them, especially for menopausal women, they are a delight,' plus, 'Highly recommend these sheets. Lovely and cool. I have tried Dunelm and John Lewis, but nothing compares. I suffer from hot flushes all year round. These make such a difference,' then my ears definitely perk up.

As a hot sleeper, I had to try the M&S Stay Cool Lyocell Rich Fitted Sheet for myself, and when I popped this sheet onto my bed last night, I soon realised those M&S reviews were right. That's because, reader, it's actually cool.

Like really cool. Not just cool for the two minutes you put your hand on it in the store and then hotter than the sun once you're lying on it at home. (Can you tell this hot sleeper is still holding onto some bedding-related 'cooling promise' trauma?).

As I write this, I'm lying on my bed, on the sheet (in the name of research, promise). I've been lying here for 30 minutes, and the sheet still feels cool.

Now don't get me wrong. This sheet isn't fridge-like. If you're someone who's currently trying to find an in-stock portable air conditioner, then, unfortunately, this sheet isn't going to deliver quite the same icy chill. But it is far cooler than any other sheet I have in my (by now extremely crammed) bedding closet.

As you'll see from the picture below, I laid my coolest fitted sheets side by side and, in a very non-scientific way, rolled from one side of the bed to the other to see which side felt the coolest.

(Don't judge me for the wrinkled bedding, it's still too hot here to iron right now, although it may be worth noting that some of those M&S reviews do mention these sheets creasing badly – personally, I'm not too fussed by that, but you may be).

The blue sheet below is the M&S Stay Cool fitted sheet; the other is a 100% bamboo sheet. The M&S Stay Cool won in my at-home cooling competition. By some margin. In fact, as I lie here, it feels like the sheet is very gently sucking the heat from my body. Which is quite an odd sensation, but as someone who's pretty much always warm in summer, it's also very welcome.

I tested the M&S Stay Cool against bamboo sheets, which are silky soft and cool to the touch, and 100% lyocell sheets, which are a little less silky but similarly cool to the touch compared to regular cotton or linen.

The M&S Stay Cool sheet is 78% lyocell (which, according to my research, is a semi-synthetic, plant-based fabric that's commonly made from the dissolved wood pulp of eucalyptus or birch trees) and 22% cotton.

According to the care label, the packaging, and the M&S website description, nothing else is added. Which is why I'm a little confused as to how it can actually be this cool. But it certainly outperforms everything else I've tested when it comes to cooling.

Did the M&S Stay Cool Lyocell Rich Fitted Sheet keep me cool all night long? No, the area of the sheet that my body was laid on did eventually warm up during the night – but it didn't get warmer than any other sheet I tested.

The difference with this M&S sheet was that I never had to move a limb too far to find an instant hit of chill again, so this sheet definitely helped me stay cooler in bed than any other.

There's some voodoo at work here, to be sure. But with another heatwave predicted for early July and still a lot of summer to go, it's voodoo I'll happily accept for a cooler sleep.

I know exactly which sheets I'll be putting on my bed when the temperatures soar next week. Thank you, M&S.