The Adventurer 1000
The Adventurer 1000 Pocket Memory is the model that carries the range and the one Which? has reviewed independently. A layer of bamboo-infused memory foam sits over 1000 individually pocketed springs. Pressure relief from the foam at the surface. Structural support from the springs underneath. The two layers work separately and you can feel both when you lie down. Medium to firm on the firmness scale. The knitted cover adds breathability at the surface, and the edge construction is reinforced for full edge-to-edge support, which is something most budget pocket sprung mattresses skip entirely.
The graphite infusion on the Odyssey 800 is the spec detail that separates it from a standard memory foam hybrid. Graphite disperses heat faster than regular memory foam, so the surface stays cooler during the initial settling period when you first lie down. It's a more credible cooling mechanism than the vague "cooling gel" claims you see on budget brands, though it still won't match the airflow of a natural fibre or latex comfort layer over the full night.
What the build tells you
A memory foam layer this thick gives you the slow, sink-in response of proper memory foam rather than the bouncy pushback of a latex or pocket-spring-only build. The foam holds your shape for a moment before releasing. Side sleepers who want cushioning at the shoulder and hip will appreciate that, but buyers who prefer a faster-responding surface will find it too slow.
Heat is the other thing to weigh. Thicker memory foam layers hold onto body warmth, and the Horizon's graphite layer is deep enough to notice. Graphite does its work on first contact; after that the warmth builds the way it does under any foam-heavy comfort layer, and I'd warn any hot sleeper off before they order.
Where to buy and trial terms
Horizon sells primarily through Mattress Online, which carries the full range with free delivery and its Comfort Trial. The trial is an exchange rather than a refund, and you need to buy a Mattress Online protector with the mattress to qualify. The Adventurer also appears at B&Q and BedBoy for buyers who prefer ordering through those channels. Pricing is consistent across stockists because Mattress Online controls the brand.
I'd pay more attention to the exchange-only terms than the trial headline. If you're confident from the spec and the Mattress Online reviews, the trial gives you a chance to confirm the feel, but it isn't a money-back option.
Who Horizon suits
Back sleepers and side sleepers of average weight who want pressure-relieving memory foam over a pocket spring base at a price below the mainstream D2C hybrids. The Adventurer 1000 is the one I'd put you on.
Budget-conscious buyers who want proper pocket spring construction with a foam comfort layer. At its price tier, the Horizon offers more spring support than pure foam alternatives costing about the same.
Who it doesn't
Hot sleepers. The graphite foam helps but doesn't solve the heat issue the way a natural fibre or latex comfort layer would. If sleeping cool is the priority, look at natural fibre brands or the D2C hybrids with dedicated cooling specs.
Buyers who want a long trial. Check Mattress Online's current terms before ordering, particularly if you want plenty of decision time or a refund rather than an exchange.
Anyone who dislikes the slow memory foam feel. If you've tried memory foam before and found the sinking sensation uncomfortable or claustrophobic, Horizon won't change your mind. The foam layer is thick enough that it defines the surface feel.
Verdict
Horizon is a focused, honest sub-brand from Mattress Online that does one thing well: affordable pocket spring mattresses with thick memory foam on top. The Adventurer 1000 is the model to look at. The range is small, the pricing is fair, and the Which? review gives it independent credibility most retailer exclusives don't have. Not the brand for hot sleepers or long-trial seekers, but if you already know you want memory foam over pocket springs without a boxed-brand price, this is a fair way to get it.
