St. Agnes' Church is roughly half way between Crumlin Cross (Ashleaf Shopping Centre) and Crumlin Village, on the left hand side of the road. Buses 150, 17 and 18 pass the door. Buses 83 (alight at Armagh Road) and 9 (alight at Ashleaf S.C.) are a 5-minute walk away!
P.S. There is also a very large free car park adjoining the church!