At the 1984 Summer Olympics in Los Angeles, Brownsdon reached the final of the 200-metre breaststroke, finishing seventh. In the spring of 1985, she won the US Short Course 200-metre breaststroke title. She then went on to finish seventh in both the 100-metre and 200-metre breaststroke finals at the 1985 European Championships. She missed out on individual medals for England at the 1986 Commonwealth Games, finishing fourth in the 100-metre breaststroke and fifth in the 200-metre. She did though, win a gold medal in the 4x100-metre medley relay, along with Caroline Cooper, Nicola Fibbens and Simone Hindmarsh. She again reached both individual finals at the 1987 European Championships, finishing fifth in the 100-metre and eighth in the 200-metre.