I stayed at Assahas for almost a week. The place has a great location next to Hyde Park and only a 15 minute walk from Marble Arch and the beginning of Oxford-street.
The place seemed even bigger in person, and that is a plus! They have a nice staff, that would clean your apartment everyday.
One bad thing that you should take within, is that the apartment is badly isolated. I froze at night even with the radiator at highest level. Furthermore you could hear everything’s that went on in the other apartments, all from them singing and yelling, to the washer being started at 7AM.
I recommend this to people who wants a good location but not families or elderly