I wonder if a single adult is allowed to stay in any Youth Hostel in London?
Is it like any other hotel where you have an option to book your own room? And how many days you are entitled to do so?Yes of course, but because it is a hostel not a hotel you book per bed, not per room.

Most beds will be in dorms, say around 6-10 beds. Hostels usually also have a few private double or single rooms but it will cost more. If you are happy sharing then you will have no problems. If there are no single rooms and you refuse to share you will have to book out every bed in a dorm or double room in order to have the room to yourself.

There shouldn’t be a time limit on how long you want to stay.

Generator Hostels Christmas Game 2010