9 best base layers and thermal clothing for keeping cosy on cold days

Although they’re available in a whopping eight colours, including blue, green and aubergine, we’ve been wearing the classic black shade. The fleece-lined trousers have a stretchy, skinny fit and we found they moulded well to our body. There’s petite, regular and long length options, in waist sizes 24-40in.

The insulating pair are shower-resistant and we did test this out on a drizzly day, to find our legs remained refreshingly warm and dry. Although billed as outdoor wear, we found the trousers looked a lot like smart jeans – so we wore them on walks, at home and out with friends too.

They made our legs feel cosy and snug, with the robust pair extremely comfy to wear. The trousers have a zip fly and belt loops, plus one of the several pockets has a zip closure. They’re structured enough to offer a flattering fit, but they’re not constricting or heavy either. In short, we have been wearing them non-stop. These trousers are undoubtedly an investment purchase, but one that will keep your legs cosy throughout winter.

This sparkly thermal top is a tight lightweight layer to pop under thicker knitwear, but we found it also doubled up as an option for a night out, paired with a skirt or trousers. There are also grey, black and navy shades – if you’d prefer a non-glittery pick. Meanwhile, sizes range from 8-22, and there’s matching Pour Moi second skin thermal leggings (£24, Pourmoi.co.uk) which we tried and loved equally too.

We found the inside of this snug-fitting polo neck has a lovely soft finish, which is comfy on skin – and that fabric effect didn’t diminish after several washes either. We found the length was suitable for tucking in, and its flattering fit created a smooth silhouette.

We instantly felt warmer after putting on this stretchy top. For less than £25, it’s a versatile number suiting both smart and casual occasions. Plus, the flecks of silver glitter add a bit of extra fun.

There are two classic shades to discover when shopping this crew neck bodysuit – we tried the timeless onyx colour. Because the item is very figure-hugging, we felt cocooned with cosiness the moment we put it on. We found it’s both stretchy and shape-fitting, and we particularly liked the chic satin-effect shiny finish.

In a crew-neck style, we found the bodysuit still covered enough of our chest to add warmth under layers, and teamed it with a big cardi when heading out to lunch on a cold day. Plus, the bodysuit element with popper fastening means you don’t need to think about tucking in any loose base layers.

We felt particularly swish when wearing this piece too, and will be looking to it for an outfit lift as well as a second-skin thermal-esque layer. There’s also a lighter ‘Sienna’ shade, which we’ve got a keen eye on too.

Currently reduced by £20, these thermal leggings have a high-waisted fit that we found kept our tummy nice and warm. Designed for wear during training sessions, we sported them during activities and when just lounging about.

The dark blue colour is a classic shade to combine with a jumper or hoody, and the full-length leg meant we didn’t have chilly ankles. We’re happy to report they kept their form-fitting shape after being washed several times as well.

The leggings are lined with thermal material, which feels both comfy and cosy. You could pop them under some baggier trousers for a long winter walk, and we paired them with thick, slouchy socks for extra snug warmth. There’s reflective strips, so you’ll be seen in the dark, and a handy phone-sized pocket on one leg too.

You can choose between a light nude, red and black sleeveless top and we alternated between a couple of these options, depending on what other colours we were wearing. The lightweight layer has a sheer effect, so it slips easily underneath most tops and tees for added cosiness. The stretchy composition also includes wool, and it’s somewhere between clothing and underwear.

Very soft to wear, it felt a comfy fit and kept our neck warm too. Part of Sloggi’s ‘thermo-regulating’ base layer range, there’s matching ever-cosy leggings (£43, Sloggi.com), which we have been wearing underneath jeans during chilly trips to the beach.

The duo is a winner for discreet layering, whether you’re heading out and about or are looking to be snug at home.

A matching top-and-leggings base layer set, this duo comes complete with signature Helly Hansen striped branding.

The mesh fabric is insulating and absorbs moisture to prevent sweat building up, which is why these pieces are popular with runners. We could feel this wearable comfort while trialling both items. Each get the right breathable balance between being a lightweight layering option and adding noticeable warmth, while we wore them mostly under jeans and jumpers.

The crew neck top sits neatly under polo neck knitwear and the leggings have a comfortable waistband. We’d wear the practical pair without other layers for outdoor activities on days that aren’t bitterly cold, too.

Silk is known for being temperature regulating, which is why it can help keep you cosy during winter. We were keen to try out a base layer made of the material, and opted for this silk and merino wool offering with short sleeves. We appreciated the top’s relaxed fit, making it comfortable to wear.

We layered it under other tops, because the scoop neck lies flat under other options. We also found the top a snuggly option with pyjamas and jogger bottoms. The blend is supremely soft to wear, and we also liked the hip-skimming length.

Available in black, oatmeal and grey, there’s a long-sleeved option too (£45, Thisissilk.com). Finally, the composition also meant this machine-washable layer dried really fast.

M&S;’s heatgen range spans across plenty of affordable thermal picks, and we particularly like this two-pack for £25. The set includes one black and one animal-print top. Meanwhile, you can shop other shades, such as grey, white and red, in the wider collection.

We found the tops to be waist length, so they either lie flat on top of trousers or can be tucked in. They’re lightweight and snug-fitting, for optimum layering, while the stretchy material added warmth under our other clothing. Plus, the scoop neck is just low enough to layer with other tops, or to pair with a necklace.

These thick thermal socks are a classic oatmeal shade, complete with orange trim for a pop of colour. Although technically classed as men’s socks, they’re a unisex one-size fit, and we’ve been wearing them for breathable warmth under wellies and around the house. The extra-long length means you can pull them up your legs or scrunch the socks down for a slouchy look.

We found the thick lining felt both soft and toasty on our feet, whether worn alone or over a thinner pair of socks. We’ve found the wool blend composition is robust enough for regular wear throughout winter too.