WITHOUT doubt, Governor Chris Patten is a wonderful host. And Lady Thatcher must have enjoyed every minute of her stay at the rambling colonial pile as his guest last week. However, for future reference, Lady Thatcher might be interested in knowing that a certain Paul Nash, formerly of her favourite London hotel, The Dorchester, is now based in Hongkong and working at one of the territory's own prestigious hotels, the Island Shangri-La. Paul, who yesterday started work as maitre d'hotel of Petrus and also the adjoining Cyrano Bar (where he'll have his work cut out keeping tabs on senior swingers like Craig Quick and Noel Quinlan, who bring riotous fun to the place with their New China Blues Agency), has had a regular association with the former British PM ever since she was evicted in tears from No 10 Downing Street 21/2 years ago. Paul explains: ''Mrs Thatcher had planned a Christmas party for her family and close friends at Chequers, the PM's country mansion. But because she was ousted as PM a few weeks before Christmas she had to find an alternative venue and chose The Dorchester.'' So, as banquet manager, Paul had the task of meeting Lady Thatcher (or the Blessed Margaret, as she was known then) to ascertain her needs. And there began their association. ''From then on, whenever she hosted a lunch or dinner I was asked to arrange it,'' says he. ''So I got to know her quite well.'' According to Paul, Lady Thatcher is ''a warm and wonderful person and not too difficult to please'' - those who served her as cabinet ministers (Chris Patten included) might beg to differ on that score! Paul also took care of the likes of Elizabeth Taylor, Tom Cruise, Charlton Heston - who, incidentally, liked to eat in the kitchens with the chef - and other assorted Hollywood egos. But Lady Thatcher was his favourite. The Lady did leave town last weekend saying she'll be coming back regularly until 1997 when she plans to be here on the (fateful?) night of June 30. So there's her dinner arrangements taken care of - right, Paul?