when you connect to kies it will tell you. no official word on uk. samfirmware are insisting that it's imminent and it has already been rolled out to romania, russia, germany (t-mobile only??) , spain and sweden if you believe the anecdotal evidence kicking around the web. personally i'm giving them till the end of april (maybe mid may) before using a rom from samfirmaware.
some people are still skeptical that it will arrive but the evidence suggests that it is at least likely and if you are unsure or not confident of the process of flashing then it is worth waiting a couple of months.