IREN WAN - LOK PING
SUNNY CHAN - LIP GUNE (NAM'S BOYFRIEND)
TONG NING - LOK YAU NAM (PING'S SISTER)
LEUNG KAR YAN - TEAHOUSE BOSS (CAMEO)
SOPHIE NGAN - JOHN'S EX-GIRLFRIEND (CAMEO)

CHRISTIAN NAME:
TONG NING - LEILA
LEUNG KAR YAN - BRYAN

HKMDB has John Liang Chia Jen as an alias for Leung Kar Yan - though I think I've heard Bryan/Brian before too.

It also has "The Postman" as an alias, which seems inappropriate