Sleepeezee ActivFlex Response 3600 Pocket Pillow Top Mattress reviewed

The Sleepeezee ActivFlex Response 3600 Pocket Pillow Top Mattress is a medium-soft, 33 cm single-sided mattress with three layers of pocket springs, ActivFlex spring foam and StayCool gel. Mattress Online lists it at a regular £1,065.63 for a double and £1,154.51 for a king at the time of writing (September 2026), and it carries a 10-year guarantee.

Three spring layers and a pillow top

Sleepeezee describes the ActivFlex Response range on its product page as the next generation of its PocketGel Plus collection. The 3,600 springs, counted in a king, sit in three tiers, and the upper two tiers use mini springs, which is where the plush, responsive feel comes from. ActivFlex is Sleepeezee’s name for a profiled gel foam that flexes with the springs.

Firmness and who it suits

Mattress Online rates the ActivFlex Response 3600 soft to medium and Sleepeezee calls it medium-soft, which we place at 4 out of 10. That makes it a side sleeper’s mattress first: shoulders and hips sink into the pillow top while the encapsulated unit keeps the edge firm enough to sit on. Stomach sleepers and anyone who wants a firm, flat surface should look at the Ultimate Ortho 2000 instead. The two gel layers and side air vents are aimed at warm sleepers, and The Sleep Charity notes that bedrooms above 24°C are likely to cause restlessness, so a cooler mattress helps most in a warm room.

Sizes, prices and weight

When we checked, Mattress Online had the single, small double, double and king on sale at £100 below the regular prices above, with a two to three week lead time. The super king was out of stock and charged at its full list price, which is why it costs far more than the king. The mattress is heavy, at 71 kg in a king by Sleepeezee’s own table, so rotating it is a two-person job; it has flag-stitched side handles and never needs turning over.

Owner feedback is solid, at 4.7 out of 5 from 43 Mattress Online reviews in September 2026. The 100-night Comfort Trial is an exchange rather than a refund, starts after 30 nights and requires a protector bought from Mattress Online. With the National Bed Federation putting the average UK replacement cycle at seven to eight years, the 10-year guarantee covers the working life most buyers will get, although it covers manufacturing faults rather than the softening of the pillow top.