Last seen for £359 at Silentnight on 2nd September 2026
Silentnight Just Sleep Relax King Size Mattress
The Silentnight Just Sleep Relax is one of Silentnight's more affordable options, available in UK Single, Double and King.
- Moulds closely to your body
- 3-zone support for better alignment
- Classic memory foam feel
Save with the previous model
Some retailers still sell the earlier version of this mattress for less than the current model's best price.
More available sizes
Last seen for £259 at Silentnight on 2nd September 2026
Last seen for £359 at Silentnight on 2nd September 2026
Last seen for £299 at Silentnight on 2nd September 2026
Mattress details
Mattress
Silentnight Just Sleep Relax Mattress
Size
Firmness
Construction
Depth (cm)
Layers
Layer Details
Key benefits
- Proper space for two: At 75cm each for two people sharing, you can both change position without negotiating, which matters when one of you gets up hours before the other.
- Extra length for taller sleepers: The UK king is 10cm longer than the UK double at 200cm, a genuine relief if either of you is approaching six foot.
- A king without a big outlay: This model sits at the budget end of the market, so it's an affordable way to move up a size rather than a luxury purchase.
- Fewer disturbances at night: The 15cm of extra width over a UK double gives restless sleepers, or a partner on a different schedule, room to move without waking the other person.
- Room for the dog: If a pet on the bed is part of the routine, the UK king absorbs that habit far better than a double does.
This size suits you if...
You share the bed every night and a double has started to feel cramped, especially if one of you is restless or keeps different hours. It also fits if either partner is tall, since the 200cm length is the quiet win here. And if you want king-size space on a modest budget, this is one of the cheaper ways to get it.
Consider another size if...
Your bedroom can't comfortably take our suggested minimum of 2.7m x 2.9m for a UK king. In that case we'd recommend the UK double instead, which needs at least 2.6m x 2.8m and still sleeps two.
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FAQ's
How big is the Silentnight Just Sleep Relax in a UK king?
It measures 150 x 200cm, which is 5ft x 6ft 6in. For two people sharing that works out at 75cm of width each. We suggest a bedroom of at least 2.7m x 2.9m so you can still open wardrobes and walk around comfortably.
Is the UK king worth it over the double for this mattress?
For most couples, yes. The UK king is 15cm wider and 10cm longer than the UK double, which you feel every night in reduced disturbance and extra legroom. Since this is a budget model, the step up in size costs less than it would on a premium mattress. Compare the live prices on this page.
Is a UK king long enough for someone over six foot?
At 200cm, the UK king gives noticeably more legroom than the 190cm of a UK single or double. For anyone approaching or past six foot, that extra 10cm of length is often the real reason to size up, more than the width.
Can two adults sleep comfortably on the king size Just Sleep Relax?
Yes, this is the size most couples upgrade to. With 75cm each you can prop pillows, shift position through the night or accommodate a pregnancy without crowding your partner, which a double struggles with. Bear in mind that construction details for this model are limited, so check the retailer's listing for firmness.
Where can I buy the Silentnight Just Sleep Relax in a UK king?
Availability for this size changes, so the most reliable answer is the retailer table on this page, where prices are updated as retailers change them. Because this model isn't widely stocked, there's limited room to shop around, but the live listing will show you the current price for the UK king.