Once you reach Carmarthen, follow the signs for town centre.  You'll know you're in the right area when you pass a bus station on your left hand side.  Follow the road past the bus station, it'll bend to the left and start going up a hill.  When you see a Monument in the middle of the road there's a turn off to your right, this is the road that the Chapel is on.  Once you're on Water St., go past Morgan's Chip shop, and the Chapel is set back from the road on the left hand side, through big black gates.  The vestry is behind the Chapel, down a lane to the right of it.