Firmness
Medium Firm
Type
Pocket Spring
Depth (cm)
33
Number of Layers
3
Trial Period (nights)
100
Warranty (years)
10
Price Range
£659
Best Sleeping Position(s)
Certifications
Assessed from the specification published by Mattress Online, captured September 2026, and from regular price comparison across our UK retail partners.
Natural fillings are the draw here. Hampshire wool and English cotton help regulate temperature, which means less of the clammy warmth some synthetic mattresses trap. The Smooth Tech™ inner-tufting removes the button-style tufts you'd find on many traditional mattresses, giving a gentler, smoother sleeping surface. Underneath, 4000 pocket springs move independently, so you get support that follows your shape rather than a flat, board-like feel. Millbrook is a National Bed Federation Approved Brand with PlanetMark Certification, and the springs' cloth pockets are made from 200 repurposed plastic bottles per mattress. If you want a British-made pocket spring mattress with natural materials at a mid-range price, this is a sensible shortlist candidate.
Key Features & what's inside
- Cover. A knitted cover that is soft to the touch, adding a layer of cosiness and warmth. It's designed to enhance airflow and breathability, which means less heat build-up overnight.
- Comfort fillings. Hampshire wool and English cotton sit beneath the cover, natural fibres that help with temperature regulation. Smooth Tech™ inner-tufting smooths the surface, so you get a gentle sleeping feel without traditional raised tufts.
- Support system. 4000 individual pocket springs, each encased in a cloth pocket made using 200 repurposed plastic bottles per mattress. Nemoflex™ technology provides edge-to-edge support, which means you can use the full width of the bed without a roll-off feeling at the sides.
Layer details from mattressonline.co.uk product page, September 2026.
Who's it NOT for?
If you prefer a soft, cushioned feel, the medium to firm tension may feel too solid, particularly for lightweight side sleepers. At 33cm deep, it's a heavy mattress to rotate, so it's less suited to anyone who struggles with lifting. It's also currently listed in UK Single only, ruling out couples.
Millbrook Smooth Tech Luxury 4000 Pocket Mattress
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How firm is the Millbrook Smooth Tech Luxury 4000?
Millbrook's product page describes it as medium to firm, so it suits most back and front sleepers, although lightweight side sleepers may find it a little too supportive. One owner reviewer did find it softer than expected, so allow a settling-in period before judging.
Does the Millbrook Smooth Tech Luxury 4000 come with a trial?
Mattress Online, the retailer listing this mattress, offers a 100-night comfort trial, but it's the retailer's own scheme rather than a Millbrook offer, and it requires you to buy a mattress protector with the mattress. Check the terms before you rely on it.
What is the warranty on the Millbrook Smooth Tech Luxury 4000?
The retailer listing describes a 10-year guarantee, structured as a 5-year warranty followed by a 5-year guarantee. That split matters, as the cover in later years typically differs from the first, so read the small print to see what's included in each period.
How deep is the Millbrook Smooth Tech Luxury 4000?
It's 33cm deep, which is deeper than many mattresses. That extra depth reflects the generous fillings and spring unit, but yes, it makes the mattress heavy to rotate, and you may need deep fitted sheets.
Is the Millbrook Smooth Tech Luxury 4000 good for hot sleepers?
It should cope well. The Hampshire wool and English cotton fillings are naturally breathable, the knitted cover is designed to enhance airflow, and owner reviews on the Mattress Online page mention good temperature regulation.
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