Billington made his international debut on 23 October 1992 at Dubai International Sevens. Of the matches he played for his national side he was on the winning side on many occasions. He played his final XVs match for Hong Kong on 31 October 1998 at Jelan Besar Stadium in the Hong Kong vs Japan match. In 1994 he scored a world record 50 points (10 tries) in a single match against Singapore in a Rugby World Cup Qualifier.
After his rugby days had passed, he taught at Hong Kong International School as a P.E. Instructor. Ashley is still teaching at HKIS , an international school in Hong Kong, as of 2016.