Really good, in my experience at least! As you might expect the uni has its own bar & kitchen places and a proper sit down Italian restaurant among other things literally on your doorstep if you live on/near campus, and although people joke about only freshers going to one of the bars the events it has have remained reasonably busy every time I've seen. It's generally a pretty good 'easy' choice if you want to go out but can't be bothered going too far afield. Regent's Canal runs right up one side of campus, so in the better weather it's really nice to just sit and chat away a couple hours by it, a lot of people I know do this and it's a really nice way to chill out without even spending much money!
There's an absolute tonne of societies and sports clubs that have regular socials, too, which also helps. The student union organises a much bigger amount of day trips, live music and comedy events and the like than I expected, too - I remember being quite bowled over early in the year when I got a copy of the union events calendar and was shocked to see that there was something cheap or free on campus I was genuinely interested in doing pretty much every week (maybe I just had low expectations though!).
There are quite a few other places you can eat or get a drink off campus but really nearby (including the old reliable Wetherspoons and this place that does absolutely AMAZING desserts), since the uni is on a road which stretches all the way along to Whitechapel station. That also means it's really really easy to get to the West End from campus.
I'm not the most prolific party animal, but there's pretty much always been something decent to do whenever I've felt like it, and everyone is really friendly. You'd be hard pushed to decide you have nowhere to go.