No bookings needed as there are agents representing various hostels on the street level.
Mirador is perceived as safer and cleaner to stay than Chungking
There is also Lucky House in Jordan - go to the Jordan MTR station take exit B (on your left-side, I think it is B1) and there is an entrance on the street/ground level - there is a hostel on the first floor - when I lived in China and use to come to HK I stayed their a few times.
you can also check out other possibilities too!
www.globalfreeloader.com www.couchsurfing.com
youth hostels 
