Campbell House is one of the worst student halls at UCL. The staff are unhelpful and will treat you badly. Cleaning stuff does a poor job and will have no problem in waking you up at 9am shouting and screaming through the corridors.
The rooms are the smallest of all the UCL halls, as well as the kitchens. Each kitchen houses 10 people but only has 2 small fridges with barely any room at all.
The only advantage is the closeness to the main UCL campus. Save your money and go somewhere else a bit further away.