Now the "European" sizes are what interests me...

I use 9x12, 13x18 and 18x24, but I'm having problems finding the bigger size without cutting it myself. Which is difficult in the dark. And then I have to load my plate holders, with a fiber plate behind the film, also in the dark.

so an order of EFKE PL25 in 18x24 would suit the bill quite exactly, I think

No, I don't believe Croatia has the highest postage rates in Europe. That "honour" surely belongs to Norway