As you will probably know by now, the Scottish Coastal Rowing Association is the class association for the St Ayles skiff, and have awarded the hosting of the 2013 St Ayles Skiff world championships to Ullapool. See www.skiffieworlds.com for more information on that.
The overall World Governing body for the sport of rowing is FISA, and they are holding the World Coastal Rowing championships in Sweden in August 2013. These championships are held in sliding seat boats, with each rower having two oars, in boats for one, two or four rowers. More information on that event can be found at http://www.worldrowing.com/news/2013-world-rowing-coastal-championships-attributed-to-helsingborg-sweden . Watch out on those sliding seats if you are intending to wear your kilts.