Is it any good?
Alpha looks worth considering on its specifications, with the Delta the stronger proposition for me. Both current models have a core of 650 pocket springs. I prefer pocket springs to open coil for a main bed, so that is a useful starting point. The choice then comes down to the comfort layers, listed firmness and whether you want a pillow top.
What I would not do is treat the word “Premium” as proof that either mattress is better than its alternatives. The useful details are more concrete: the Delta is listed as medium to firm and 25cm deep, while the Kappa Black is medium and 30cm deep. Those differences tell you more about which to investigate than the model names do.
The range
The Alpha Delta Premium Mattress is the simpler option. Its listing describes a pocket-sprung core with foam and fibre comfort layers, while Mattress Online lists soft white fibres and a medium-to-firm feel. At 25cm deep, it is the shallower of the current pair. I would put it first on the shortlist for someone who prefers a firmer description and does not want an added pillow-top finish.
The Alpha Kappa Black Pillow Top Mattress is the deeper, more cushioned-looking alternative, with a medium firmness description, memory foam and a 650-pocket-spring core. Its 30cm depth and full black cover distinguish it from the Delta. It is the one to investigate if memory foam and a pillow top are specifically what you want, rather than simply assuming that deeper means better.
You may also come across the Alpha Theta Premium Pillow Top Mattress when searching. Mattress Online has stopped selling it, and as another pillow top it would not have made my shortlist anyway.
Becky's reasoning for her picks
The Delta gets my recommendation because it is the closer fit to what I would choose for a straightforward main bed: pocket springs, a medium-to-firm description and no pillow top. If you already know you dislike a firmer surface, its medium-to-firm description is a reason to pause.
I would not make the Kappa Black a second pick simply to offer more choice. I generally avoid pillow tops, and there is a non-pillow-top option in this range. Its black cover is distinctive, but appearance would not persuade me to choose a construction I do not favour. Someone who actively wants memory foam beneath a pillow-top finish may reach a different conclusion.
What owners say
One owner of the Alpha Delta Premium Mattress says that they and their partner were impressed with its comfort and how well they had slept after delivery. It is an encouraging start for a mattress two people share.
Buying it
Mattress Online sells Alpha in sizes from double to king. Its brand page states that every Alpha includes a warranty. Mattress Online's comfort trial covers it too: if the mattress isn't right, you can exchange it for another, as long as you bought a Mattress Online protector with it.
The product listings describe delivery to the front door of your building, with a two-hour delivery slot provided the day before and a call on delivery day. Room-of-choice delivery and old-mattress recycling are separately charged services. If the mattress has to go upstairs, add room-of-choice delivery when you order.
