Its at the Nautical college next to the river.
If you head towards the river then follow it east (up river) until you see a golden dome Its the next building along from it. It has nautical things all over it.
The actual exams are in the building next door across the road which goes over the bridge. You have to go behind the swimming pool then through the main door. The exam room is on the first floor at the canteen turn right i think then up the stairs.
Good luck
MJ