Caledonian Seaplanes were victims of the winter storms and as of mid-february appear to be without an aircraft. I assume if the position had changed their web site would have been updated -
http://www.caledonianseaplanes.co.uk/news/3/16.html.
So if you are looking to do it soon Neil or TAFC at Enniskillen are probably your best bet. Not flown with TAFC but can recommend Neil.
Is there not somebody down south with a Cessna 182 on amphibious floats proposing to offer ratings? There was an article about it in Pilot a few months ago. Might be closer to home.
g45