McClatchey represented Scotland in the 1974 British Commonwealth Games in Auckland, New Zealand. In 1975 he swam for Scotland at the Three-nations tournament in Prague, Czechoslovakia and at the eight-nations swimming tournament in Mallorca, Spain. He won a silver medal at the 1975 World Championships in Cali, Colombia as part of the British 4 × 200 m freestyle relay with Gordon Downie, Brian Brinkley and Gary Jameson In 1976, apart from winning a bronze medal at the Olympics, he broke the British records for the 400 m freestyle, the 200 m butterfly and the 400 m individual medley, the latter while swimming for Great Britain at the Europa Cup in Italy. He also swam for Britain in the 1977 European Aquatics Championships in Jönköping, Sweden, won seven Scottish and seven British championships that year and represented Scotland at the annual eight-nations match. He represented Scotland at the 1978 Commonwealth Games in Edmonton, Alberta, Canada and at a four-nations match in the Netherlands the same year. McClatchey again represented Scotland at the eight-nations tournament in 1979, broke the Scottish record for the 100 yards butterfly and swam in the 1979 Summer Universiade (World University Games) in Mexico. In 1980 McClatchey swam for Scotland in the eight-nations match (at the Royal Commonwealth Pool in Edinburgh) for the last time and also represented Scotland at an international match in Bremen, Germany.