Hey Dan,
don't want to discourage you at all, but 23k/month is not a lot of $ if no housing allowance is included in the package. rent will set you back in the vicinity of 10k/month.
also, if your GF is a qualified teacher, she should be able to get a higher pay than just 23k - that's almost the same pay you'd get if you did as jimbo suggested and got a TEFL and taught english in a college with no other qualifications (apart from a degree of somesort).
you can come here on a tourist visa and check it out, and you can leave HK for a day (Macau or Shenzhen) and re-new that visa once or twice without hassle (for UK i think you'd get a 90 day visa).
in regards to bar work - to get a work permit in HK i think you have to be able to have a sponsor/employer that will state that local talent cannot fill the position - but there are some bar positions that "could" be put in that catagory
but hang it - come to HK! even if your GF "only" gets 23K - if you get your TEFL etc and get some teaching work, between you both you're bound to have enough cash for some fun!
HTH,
DDF