Hypnos Cawthorne Extra Firm Super King Mattress
The Hypnos Cawthorne Extra Firm Mattress has 1000 ReActive pocket springs under a wool and polyester comfort layer, which means you get very firm, level support with a little cushioning on top.
- Extra-firm feel for back sleepers
- Edges reinforced with firmer springs
- Wicks away moisture as you sleep
£1,009
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Hypnos Cawthorne Extra Firm Mattress
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Mattress details
Mattress
Hypnos Cawthorne Extra Firm Mattress
Size
Firmness
Extra Firm
Construction
Pocket Spring
Wool
Depth (cm)
26
Layers
4
Layer Details
Pocket spring core
A core of 1000 ReActive springs, each enclosed in its own fabric pocket. Each spring works independently, so the support follows your body rather than moving as one block.
Dual density eOlus fibre pad
A dual density fibre pad that supports the spring unit and helps spread pressure evenly. That means your weight is shared out across the surface rather than concentrated in one spot.
Wool and polyester comfort layer
A blend of wool and polyester fibres that adds comfort and enhances the firm feel. You get a little cushioning without losing the extra firm character.
Cotton and polyester layer
An absorbent blend of cotton and polyester that wicks moisture away from your body. It helps the surface feel drier through the night.
Layer details from mattressonline.co.uk product page, November 2026.
Key benefits
- Distance from a restless partner: You get 90cm each, and the 1000 springs sit in their own pockets, which means a partner rolling over at 3am is far less likely to disturb you.
- Space when the bed fills up: A child arriving after a bad dream or a large dog settling in still leaves the adults a usable share, and the reinforced edge feels secure for whoever ends up outside.
- 15cm more each than a UK king: Moving up from the UK king adds 30cm of width but no extra length, so you gain sleeping room without the bed reaching further into the room.
- Proportioned for a large master bedroom: In a period property or a generous master bedroom, a UK king can look slightly undersized, whereas 6ft of width fills the space and suits it properly.
- Consistent feel across a wide surface: The dual density fibre pad spreads your weight over the spring unit, so the extra firm feel stays even wherever you lie on this large bed.
This size suits you if...
You share the bed with a partner who tosses and turns, or children and a large dog regularly join you overnight, and you want an extra firm surface with enough width that nobody is squeezed to the edge.
Consider another size if...
Your bedroom is under our suggested 3m x 2.9m, or your doors and landing are tight. We'd recommend the UK king instead, which needs at least 2.7m x 2.9m.
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FAQ's
What size room do I need for a Hypnos Cawthorne Extra Firm super king?
We suggest at least 3m x 2.9m for a UK super king, and around 3.5m x 3.2m feels more comfortable. Check the door swing and the turn at the top of the stairs too, because a 180 x 200cm mattress is awkward to manoeuvre through a narrow landing.
How much wider is a UK super king than a UK king?
The UK super king is 30cm wider than the UK king, and both are the same length. Shared between two, that works out at 90cm each against 75cm on the UK king, so each of you gets 15cm more. The UK king needs a room of at least 2.7m x 2.9m.
Is a super king big enough for two adults and a child?
For occasional night-time visits, yes. With 90cm each, a small child can settle between you without either adult being pushed out. The Cawthorne's edge is reinforced, so the person on the outside should feel secure near the side rather than as though they might roll off.
Will I feel my partner moving on a super king pocket spring mattress?
Much less than on a narrower bed. You each have 90cm, and the Cawthorne's springs are individually pocketed, so they respond separately rather than as one unit. Yes, a very restless partner may still register occasionally, but the extra width does most of the work here.
What bedding fits the Hypnos Cawthorne Extra Firm in a UK super king?
You'll need UK super king fitted sheets and a 260 x 220cm duvet. The mattress is 26cm deep, so choose fitted sheets with a pocket deep enough to tuck well under it. Super king bedding costs more than smaller sizes, so factor that into your budget.