LONG after the British Garrison has left Hong Kong, its jeeps will be roaming the streets of China, and armoured cars transporting gold bullion in Papua New Guinea. As the countdown to 1997 begins in earnest, with the Army Air Corps 660 Squadron officially stopping flying on Friday, more and more army surplus will be going under the hammer. Already, 40 of the 43 Saracen armoured vehicles have been sold following the disbanding of the Saracen troops in March. Three went to Papua New Guinea to be used as carriers in the country's gold industry. The rest are with private collectors in Australia. Five of 660's Scout helicopters were sold for US$100,000 (HK$772,000) to a British dealer last week. And Land-Rovers, military coaches and staff cars are being sold to dealers from the mainland, mostly for scrap, but a few will make it on to the streets. However, it will be the nuts and bolts, army watches, spent cartridge cases, bookshelves, uniforms, carpets, cutlery and maybe even the kitchen sinks that will make next year the busiest for the supply services. ''As we pull out, the sales will be increasing in scale,'' said Major Mike Edwards. Under the Defence Cost Agreement, the Hong Kong Government picks up 65 per cent of the sales, the rest going to Britain. This year, disposals fetched $2.27 million. Warrant Officer Billy Williamson of the Return Stores Group said that stores other than Blackdown Barracks were being sought to cope with next year's surplus.