JOINING the long queue of foreign insurers anxiously waiting to enter the China market, Australian life insurer National Mutual, parent company of Hong Kong-listed National Mutual Asia (NMA), opened a representative office in Beijing this week. ''While you can consider Hong Kong as National Mutual Asia's home, China is its future,'' said John Snelgrove, general manager of marketing for NMA. Lured by the huge potential of the China market, about 40 foreign insurers have established representative offices there. With the exception of the American International Group which has been licensed to operate in Shanghai, others can only wait by the sidelines. ''One piece of good news is the recent change in regulations governing foreign financial institutions. The time span for upgrading from an office to a branch has been shortened from three years to two,'' said Joseph Sin, general manager for China for NMA. The company was considering an operations base in Guangzhou and Shenzhen, but the ambiguity in existing insurance regulations posed a major difficulty to expanding into the market, he said. NMA, which will announce its interim results next week, will be accounting for a fall in sales force to about 2,600, after losing 650 to a competitor. NMA is launching a new marketing drive by offering free insurance policies to policy-holders to commemorate its 125th anniversary. New clients who take out life policies before the end of September will enjoy the same benefit.