Also M&S here. One pair was given to me about 5 years ago and worn at least 3 days a week for two years straight. Now they are worn in but can still be worn outdoors though mostly worn at home. Best pair i have ever owned.
I have some uniqlo heatech for winter that i mostly wear like thermals under my jeans. Cant feel even a tiny bit of cold when worn this way and they aren't bulky at all.
someone on a different thread posted about a site called everything £5.00 which sold nice leggings, i bought a pair and they are slightly fleecy lined so warm and soft,thick and nice for £5 got an amazing hat at the same time