Coastal Skipper / Yachtmaster Examination
The best advice I can give you is to refer to the RYA Sail Cruising Scheme Logbook - G15/04, available from chandlers. You should have a copy of this already no doubt as proof of your seatime. Be aware the latest edition has a couple of extra topics, namely use of electronic navigation, waypoints / routes, danger of lee shores, ability to skipper a yacht and manage the crew, all berthing and unberthing in a variety of conditions. Check out the latest edition if you don't have it.
You can take the exam in your own boat and book Examiner direct. See www.rya.org.uk for up to date info.