HAD a revealing Sunday brunch with Patti Mostyn, Elton John's formidable Aussie PR minder who has been by his side for 20 years keeping troublesome hacks at bay. Forget about sex, drugs and rock 'n' roll, as used to be the case with Elton's travelling show. Sex and drugs have been firmly replaced by tennis and muesli - as I discovered when chatting to Patti. ''Those of us who have worked closely with Elton for so long are like a family. We always do things together,'' explained Patti, who left for Singapore yesterday afternoon with Elton for the last two concerts of a world tour that started last May. ''But we've all got a lot more sensible. Now it's no sugar, no fat, no full cream milk or cheese, and plenty of exercise.'' After the Singapore concerts, Elton and his aides will board a flight to Los Angeles and the pop star will celebrate his 46th birthday in the air. During his Hongkong sojourn, Elton developed a taste for Chinese ceramics and spent a tidy sum on some exquisite items. Said Patti: ''Manager John Reid and I also bought him some small pieces as a birthday gift.'' The only other bit of serious shopping that Elton did was in the Gianni Versace boutiques at The Peninsula and The Landmark. Lamented Patti: ''There was a beautiful Versace jacket at The Landmark shop which Elton, in a moment of generosity, offered to buy for me. But, just my luck, they didn't have it in my size.'' Of Elton's current rock status, Patti said: ''Elton now seems to have widened his appeal. Those who attend his concerts these days represent all ages and different walks of life.'' The latter point was driven home to me by a conversation I overhead between two expatriates at one of Elton's concerts at the Coliseum. Expat one: ''I've never known a pop concert where I've seen so many High Court judges. I've already spotted four.'' Expat two: ''That's quite amazing. You'd never dream of seeing High Court judges at pop concerts in England.'' Expat one: ''That's true. You're more likely to bump into them at the karaoke bar at Miss Whiplash's place.''