I spent 2 nights at the Steam Engine. People at the pub arevery nice. The hostel upstairs is very well secured (you need an electronic card to enter the hostel and then the room you stay in), you have a locker in the room (for which you'll have to take a padlock if you want to secure it) to put your things in. There's 9 beds in each room, and 4 showers for about 40 people. I was afraid I'll have to wait forever to take a shower, but whenever I went there, there was at least 1 shower available! I never waited!
It's a bit hot in the bedroom (considering the thickness of the duvet) when I was there (end of June) especially when you're on the top bed but it remains bearable. There's noise coming from the outsideat night (sirens wailing for most of it) when the windows are open.
The pub is at five minutes from the Underground and near a lot of curiosities. I managed to walk from the pub to Oxford St and Hyde Park and then get back on foot.
When leaving, you can secure your luggage in the luggage room (my train was at 3pm so I left my suitcase in the luggage room from 9am to 1pm and it was no trouble for them).