I decided to take the plunge and flash ICS on this phone.
I initially though that the O2 ROM would be good since it would at least come up on English so I could choose the other language. With some trepidation flashed the ROM, waited for the success message and the phone powered up, upgrade apps etc. and then had ICS. The startup animation has some O2 logo and the background wallpaper appeared to be some London landscape (not surprising I guess).
Success I thought and I went to select language only to find the same set that Telecom has - a whole bunch of language but no Asian language apart from Korean (not surprising given the phone is Korean).
That was annoying so I decided to flash the HK ROM. Again the flash went fine but this time on reboot there was no carrier logo or customisation and there was no upgrading apps message. Went into the language option and this time there were 2 Chinese language options (thank goodness), for simplified and complex form (mainland China and HK), English (UK, US) and Korean.
The phone seems to work fine after that with my putting it a 2D SIM and making and receiving a call successfully.
Thanks to all who helped on the forum.