We happily stayed at the Holborn apartment for 4 days. The best thing to highlight about the flat was the location. It easily fitted 3 people sleeping there. It also comes with all the kitchen stuff needed.
Also notice that the out of hours checkin is £60, this was arriving at 8pm on Monday when their closing time is at 6pm which is something that I think is really expensive.
In general I recommend to stay at this apartment to have a good London experience.