Is London hostel culture in February is a bit dead?

I can make it to London in February and would like to stay in a hostel, but everyone always says London (and everywhere in Europe for that matter) is so terrible in Europe, but well it's the only time that works for me. I've already been southern spain and all that where its warmer, so I don't mind the cold.

Everyone says Onefam Notting Hill is the best, which I'd book, but is it dead during this time? I'm also 23, so I'm not sure if Im too old if its a super college 18-21 type of vibe?