MOST letters I receive that are posted from Kowloon/New Territories take about five or six days to arrive at my apartment in Repulse Bay. Mailings from Hong Kong side are usually prompt, within one or two days. However, the situation of late is getting worse! My monthly statements from Park'N Shop and Wellcome Supermarket received on February 28, were posted on February 9 (from Sha Tin Central) and February 14 (from Hong Kong), respectively. These post office delays put me in an embarrassing situation as the Park'N Shop statement was to be settled by February 20 and the Wellcome statement by February 22. I now must explain to both companies why I missed the deadline. Can the Post Office shed any light? A particular concern among many people seems to be the delay in Kowloon/New Territories mail reaching Hong Kong Island. JOHN McCARTHY Repulse Bay