Last month I went to
Air Hart Aviation in Kelowna, BC to do exactly what your planning - and one of the very very few places I found that lets you hire solo once you've got the rating. See my
thread .
All you need to do is take your JAA/CAA license to a Transport Canada office with your medical and passport, pay them CAD40, get a temporary Canadian license (valid for 30 days I think and not renewable within the next year), do 5hrs dual and 1hr solo, go backk to the Transport Canada office, pay them CAD30 to get your temporary license endorsed with the Float Rating, go do as much solo time as you want within the remaining ~30days, come back to UK, sit Seamanship exam (details in LASORS), pay UK CAA for seaplane rating and hey presto you're fully signed up! Simple eh? The usual simple unbureaucratic procedure!