🔥 This mattress topper uses a heat-reflecting foil layer to retain body warmth, eliminating the need for electricity. 🛏️ Lidl introduces the Silentnight Self-Heating Mattress Topper, available from 8 February, priced at £25.19 for Lidl Plus members. 'The Silentnight self-heating mattress topper features a unique heat reflecting foil layer combined with a thermal lining and deeply filled quilted top layer to add up to 7.5 tog of extra warmth to your bed,' says Lidl. The self-heating mattress topper is just one of the items in the retailer's latest bedroom collection. 5 FAQs about the self-heating mattress topper1) What is it?