You are referring to Champagne Court in Kimberley Street. It is great if you want to see a lot of old cameras but be ready to negociate! Speaking cantonese is a plus there...
Other shops like Tin Cheung Camera are ok but not always friendly. Shogun Camera in Lock Road (Tsim Sha Tsui) is also ok. There are other shops around Shogun Camera but don't know their names.
There are more shops in Tsim Sha Tsui area like Ninedays, Photopia, C9.99, etc... but I don't know where they are located exactly. I am sure Wongsan sifu and Gommy can help with the addresses...
Old leicas, rolleiflex, hassy are not cheap but MF camera like Bronica SQ, Mamiya C, Mamiya 67, etc... are very reasonably priced.