CAT'S MEOW Retiree Bob Martin thinks London's longest running musical is so purr-fect he has seen it 625 times (so far) During the last decade, Bob Martin has traveled enough miles to have take him around the world at least four times. But far from trotting the globe, Martin, 69, has simply been making the 180-mile round-trip in the southern English town of Eastleigh and London's West End to lap up yet another performance of the Andrew Lloyd Webber musical Cats. "I'm not obsessed," Martin insists, while admitting that he has spent more than $23,000 on orchestra tickets to the show. "Something about the show just clicked," says Martin, who finds inspiration in the musical's upbeat story line. "Nothing has ever affected me as much." The never-married, retired cable factory worker had never seen a musical (or, for that matter, owned a cat) until 1988, when he checked out the show's original cast recording from his local library. Since then cast and crew have come to treat him like an adopted stray, even inviting him to cast parties. "[He] has become sort of everybody's grandpa," says company manager Philip Effemey. Adds Heather Douglas, who plays cat Bombalurina: "It's amazing someone knows the show so well." "This Cats thing is weird," admits Martin's niece Kate Clayton, 47. But, says another niece Barabara Paddock, 40, it "keeps him young." Martin says he has enough other interest - including World War II and supernatural occurences - to sustain him when Cats finally runs out of lives. And, he allows, there's one more thing he will have: "A lot more money."