Firmness
Firm
Type
Orthopaedic
Depth (cm)
26
Number of Layers
2
Trial Period (nights)
100
Warranty (years)
5
Price Range
£339 to £635
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.
If you sleep on your back or front and want firm support at a sensible price, this is the sort of mattress to shortlist. The PostureTech Core Support Springs use varied tensions and unique shapes, which means different parts of your body get support matched to the pressure they place on the mattress. A layer of soft white fibres sits above the springs to cushion hips and shoulders, so it's firm without feeling bare. It carries reassuring credentials too: National Bed Federation approved, fire resistant to BS7177: 2008, and 100% recyclable at the end of its life. Yes, it's a simpler build than pocket sprung or hybrid designs, but that simplicity keeps the starting price at £339.
Key Features & what's inside
- Comfort Layer. Soft white fibre fillings sit at the surface to cushion the hardest parts of the body, which means your hips and shoulders get a little give before reaching the firmer support below. It's a traditional filling with a slightly springier feel than foam.
- Support System. PostureTech Core Support Springs use unique shapes and varied tension across the mattress, which means fuller support where your body presses hardest and pressure relief where it doesn't. This is the layer doing most of the orthopaedic work.
Layer details from mattressonline.co.uk product page, September 2026.
Who's it NOT for?
Lightweight side sleepers may find a firm orthopaedic feel too unyielding on the shoulder and hip. Across owner reviews, some mention concerns about edge support, so if you sit on the side of the bed a lot, that's a weak spot. And if you love a deep, cradling memory foam feel, this isn't it.
Sealy Harlow Ortho Plus Mattress
Across 353 reviews on the Mattress Online product page it holds a 4.5 rating, with owners commonly describing a comfortable sleeping experience best suited to back or stomach sleepers. Some found it softer than expected, and a few raised concerns about edge support and slow rebound.
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Is the Sealy Harlow Ortho Plus firm?
It's listed as firm, and it's an orthopaedic design, so expect a supportive feel rather than a soft one. That said, some owners in reviews found it a little softer than they anticipated, so the fibre comfort layer does take the hard edge off.
Does the Sealy Harlow Ortho Plus come with a trial?
Mattress Online, the retailer that stocks it exclusively, lists a 100-night trial and a 5 year guarantee. These are the retailer's own terms rather than a Sealy promise, so check the details at checkout.
Do you need to flip the Sealy Harlow Ortho Plus?
No. It's a single-sided mattress, so there's no flipping required, which is welcome given firm orthopaedic mattresses can be heavy to handle.
How deep is the Sealy Harlow Ortho Plus mattress?
It's 26cm deep, a fairly standard depth that should work with most fitted sheets without any struggle.
What sizes does the Sealy Harlow Ortho Plus come in?
Five UK sizes: Single, Small Double, Double, King and Super King, priced from £339 to £635 depending on the size you choose.
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