Firmness
Medium Firm
Type
Pocket Spring
Depth (cm)
29
Number of Layers
4
Trial Period (nights)
100
Warranty (years)
5
Price Range
£679 to £1,199
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.
The main draw here is the spring count paired with natural fillings. The 4,000 pocket springs adapt to your movements independently, which means better support along your spine and less disturbance from a partner. Wool sits above the springs, a fibre that helps regulate temperature, so hot sleepers should find it more forgiving than foam. Note that the listing states this mattress as firm, so it suits back and front sleepers, and heavier bodies, better than lightweight side sleepers. It carries a 5-year guarantee, is a National Bed Federation approved brand, and Mattress Online lists a 100-night trial with free delivery to most locations, so there is a reasonable safety net if the feel isn't right.
Key Features & what's inside
- Cover. A viscose cover, a soft breathable fabric, finished to a high standard. It gives the sleeping surface a smooth, cosy feel.
- Wool. A plush layer of wool fibres for a luxuriously cosy feel. Wool also naturally helps with temperature regulation, so it tends to suit warmer sleepers.
- Soft White Fibres. Soft synthetic polyester fillings layered on top of the springs for extra comfort. These add a gentle cushioning between you and the firm support below.
- Pocket Springs. The core is 4,000 pocket springs, made from twice tempered steel, that adapt to your shape and movements. Each spring moves independently, which means personalised support and less motion transfer across the bed.
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Layer details from mattressonline.co.uk product page, September 2026.
Who's it NOT for?
This is a firm mattress, so lightweight side sleepers may find it presses on the hips and shoulders rather than letting them sink in. If you love the slow, contouring hug of memory foam, the springy, traditional feel here won't give you that. Budget shoppers may also find the larger sizes, up to £1,199, a stretch.
Wentworth Mercer Deluxe Wool 4000 Pocket Mattress
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Is the Wentworth Mercer Deluxe Wool 4000 firm or medium firm?
The product listing rates it as firm, though you may see it described elsewhere as medium firm. Treat it as a firm mattress: good for back and front sleepers and those who like solid support, less suited to lightweight side sleepers.
Does the Wentworth Mercer Deluxe Wool 4000 come with a trial?
Mattress Online lists a 100-night trial on this mattress. That trial is the retailer's own offer rather than a manufacturer promise, so check the terms wherever you buy. The mattress itself carries a 5-year guarantee.
How many springs does the Deluxe Wool 4000 mattress have?
It contains 4,000 pocket springs made from twice tempered steel. Each spring moves independently of its neighbours, which means the mattress adapts to your shape and reduces the ripple effect when a partner moves.
What sizes does the Wentworth Mercer Deluxe Wool 4000 come in?
It's available in UK Single, Small Double, Double, King and Super King, priced from £679 to £1,199 depending on size. The mattress is 29cm deep, so check your fitted sheets will stretch to a deeper profile.
Is the Wentworth Mercer Deluxe Wool 4000 made in the UK?
Yes, it's handcrafted in the UK, and Wentworth Mercer is a National Bed Federation approved brand. It also conforms to BS7177: 2008 fire resistance standards for home use.
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