Bed sheets are sold as fitted (with elasticated corners), flat (rectangular sheet to tuck), or as part of a duvet set. The British convention is fitted-and-duvet without a flat sheet; the European convention is flat sheet under the duvet. Aosom UK, Fulfilora and La Redoute UK between them cover £4-£100 across the range. Cotton dominates the household sheet market: percale weave (smooth, crisp, sleeps cool); sateen weave (silky feel, slightly warmer); flannel cotton (brushed for winter warmth). Thread count above 200 in pure cotton is a meaningful upgrade in softness; above 400 is largely marketing. Bamboo and Tencel sheets are the eco-friendly option, sleep cool, and resist allergens; they cost £30-£80 more per set than cotton. Skirt depth on fitted sheets matters more than thread count: 30cm skirt fits most domestic mattresses; 35-40cm skirts cover deeper mattresses and topper-stack mattresses.