Hi,
I know it's your first post, I'm not sure how much or little time you have flying. You could buy either of the two aircraft you mentioned, and make it work no doubt. If I had that budget, I would call Paul Furnee the 18,000hr seaplane expert and have him fetch me a nice Lake Renegade and have him ferry it/box it and re assemble it. Then let him show you how to do it safely. Winds/WX/Loads much less of a factor to a Lake. I've owned and flown them and miss my old one alot. For half the money you could buy a LA4-200 EP which will do 80% as much.
Before I'd spend all that money I'd get a UK based seaplane owner or operator to do the trip with me a few times in their aircraft and see if it works in practice.
Enjoy,