GLAMOUR cat Jacintha Abisheganaden - who quite helpfully asked Keeping Posted to just call her ''Ja'' - breezed into town yesterday to announce the fact that Polygram is releasing a commemorative compact disc of Cats to celebrate the musical's eagerly awaited January opening in Hong Kong. Singaporean Ja, who has a haunting version of the show-stealing Memory on the CD, broke off from rehearsals back home for the musical's opening there later this month. Incidentally, if you fancy attending the opening night of Cats as the guest of the producers, The Really Useful Company, then get your thinking caps on. RUC managing director John Duffus is searching for a suitably catty (now, now, not so fast . . . ) phrase to use as the theme for the evening. And the person who comes up with the best offering, together with a partner, will be VIP guests on the night. But, please, direct your catty remarks not to us but to Duffus on 369 7923.