Slumberdown Sleep Soundly 10cm Extra Deep Mattress Topper reviewed

The Slumberdown Sleep Soundly 10cm Extra Deep Mattress Topper is a box-quilted hollowfibre topper made in the UK, sold in a Classic version from £30.20 for a single and a Climate Control version for people who sleep warm. It is one of the easiest 10cm toppers to keep clean, because it washes at 40°C and can go in the tumble dryer.

Construction and the two versions

The Slumberdown product page describes a 100% microfibre cover, box-stitched over a plush hollowfibre filling designed to bounce back, with strong elasticated straps that fit a range of mattress depths. The Climate Control version uses a synthetic filling treated with Dacron, which Slumberdown says draws excess moisture away from the body to keep you cool in summer and warm in winter. That is the maker’s claim, and Slumberdown publishes no measurements to back it.

Slumberdown is owned by the John Cotton Group, established in 1916, and according to Slumberdown’s about page its pillows and duvets are made at the group’s head office in Mirfield, West Yorkshire. The topper page states that Slumberdown products are designed and made in the UK.

Prices for both versions

Regular prices on slumberdown.co.uk, checked on 28 September 2026, with free standard delivery. Climate Control costs between £14.80 and £24.90 more, depending on size.

Washing, allergies and who it suits

The 40°C wash is convenient, but for a dust mite allergy it is a compromise, since Cambridge University Hospitals advises washing bedding on a 60° cycle and says “A cooler wash will only partly kill the mites”. Being able to wash and dry the Sleep Soundly in one day does make regular washing realistic, which counts for a lot with a fibre topper.

Like any 10cm hollowfibre topper, it softens rather than supports and will flatten with use, so Slumberdown’s line that it adds support is generous. It suits a firm mattress or a spare bed at home, and Slumberdown itself pitches it for caravans, motorhomes and camping trips. Choose the Classic unless you regularly wake up too warm.