The Silentnight Bonnell Mattress is a spare-room mattress, and I'd only buy it for a bed that sees a guest a few times a year or for a budget that can't reach pocket springs. A bonnell open coil, one unit of springs wired together, sits under a thin fibre top, graded Firm and rolled up for delivery. If you share a bed, sleep on your side, or want this to be the mattress you sleep on every night, walk past it.
One wired unit, so the whole bed moves together
Bonnell springs are formed from a continuous steel wire and interlaced into a single lattice. Press one spot and its neighbours go down with it. That's why a partner rolling over reaches your side, and why an open coil tends to dip where you lie most nights. My worst bed was this kind of unit, an old Silentnight hand-me-down that was already twenty years old when it reached me, with a divot between the springs that I slept in for years. That was a tired old open coil, not this one, but the design keeps the same habits.
On top there's a tightly packed layer of polyester fibre, then softer white fibres and a knitted cover. No foam anywhere, which keeps it cooler than a memory top and keeps the price down. It also means the springs aren't far from you. Mattress Online gives the depth as 19cm in one place and 19.5cm in another, about 7.5in, so standard fitted sheets go on easily and there isn't much padding in there. I've never found Silentnight an exciting brand, but for once the name is honest: Bonnell is exactly what you get.
A guest bed for back sleepers, and not much else
Buy it for the spare room if your guests mostly sleep on their backs, or for a first flat where the alternative is somebody else's old mattress. Firm on an open coil is a reasonable spec for a bed that's used a few nights a year. It arrives rolled, so it goes up a narrow staircase without a fight.
Avoid it if you sleep on your side, because a firm coil under a thin layer of fibre pushes back hard at the shoulder and hip. Skip it too if you're over about eighteen stone: Silentnight publishes no spring count or wire gauge, and a heavier body needs a unit you can judge on paper. It's one-sided, so rotating it head to foot every few months is the only care it takes, and I'd always rather have a mattress I could turn. Would I buy it for my own bed? No.
Most of the reviews describe the earlier model
Read the reviews with care. Most of them were written about the Silentnight Amsterdam Miracoil Ortho that this listing sold for years, a deeper, extra firm mattress on zoned Miracoil springs. Even so, the complaints in those older reviews match what a firm open coil does. Too hard is the one that comes up most; next come springs felt through the padding, then squeaks and a bounce that travels across the bed. One recent owner put it as "too hard and absolutely no give".
The older reviews, for the earlier model, say the people who wanted a hard bed got one. Firm suits some backs, but harder isn't automatically better for one, and medium-firm on pocket springs is where I'd start most people.
What to buy instead
For an everyday firm bed from the same maker, step up to the Silentnight Air Plus 1000 Mirapocket: also graded Firm, but on pocket springs that move one at a time, so you feel far less of your partner. For a spare room, the Bonnell does the job, and I'd spend what's left on a decent pillow for the guests.
