I have just returned from my vacation to HKG and BKK, very enjoyable!
I bought a phone card on the recomendation of an ex-pat from a small store.
The phone card stated just over 1 hour to the UK for 50hkd less 10% discount=45hkd, the actual time lasted around 15 mins! but this was about 1515hrs local.
I suppose it was still a lot cheaper than phoning from my hotel room.
Incidentally, I eventually stayed at the Grand Stanford IC, a full harbour view room was around 170 usd, the view was slightly obstructed by the rail tunnel works, a small amount of noise also, however the passing road traffic is quite noisy.