Great. I have one of the Silentnight Studio mattresses for a double bed, and this is similar, if a bit softer.
For a single bed I would say this is firm enough, most singles will be used by lighter people.
For a double, I'm not sure it would qualify as Medium/Firm, more Medium.

The quality of the mattress is excellent.
As with all of these, if you can avoid sleeping on it for the first week that's better - memory foam mattresses all smell when they first unroll. I've had four, and this is no better or worse than any of the others. The payoff in terms of comfort is well worth it.