SALES of the new BMW Series 3 and buoyant interest in the European Ford range boosted net profit at Sime Darby Hong Kong by 30.44 per cent to $246.8 million in the six months to December 31. A drop in imports to China, anticipated tax changes surrounding China trade and a strong Japanese yen would affect group prospects in the second half to June, the company said. Earnings per share came to 52.9 cents, up 30.3 per cent, compared with $1.085 cents in the full year in 1993. A dividend of 20 cents was announced compared with 16 cents in the first half of 1993, and $1.41 cents for all of 1993. Owned 74.9 per cent by Sime Darby of Malaysia, the group traditionally has a high dividend payout policy. ''In the period under review, the Hong Kong economy remained buoyant despite political uncertainties,'' the company said. ''Total vehicle market registrations dropped by five per cent, with a marginal increase in the passenger car market and a decline in the commercial sector.'' The interim result compares with 24 per cent net profit growth at the interim stage of 1991-92 to $189.2 million. In 1992 the interim result represented 37.4 per cent of full-year net profit and in 1991 it was 59.5 per cent. The Estimate Directory indicates the consensus broker profit forecast for the full year to June is a one per cent rise in net profit to $510 million and earnings per share at $1.07, down one per cent. For 1995, analysts are expecting net profit at $580 million, up 14 per cent and earnings per share at $1.24, up 16 per cent. The company said in the first half of the 1993-1994 period, China Engineers Construction benefited from the demand created by the new airport and a strong order book for China. ''Motor vehicles sales to China have been affected by the reduction in imports during the first half of the financial year,'' Sime Darby said. ''The company is committed to developing its core activities into the southern provinces of China.'' and will be investing to support this strategy.''