You are correct. The only difference between the UK and SE/FI Filco should be what is painted on the keys. You set the keymap in the OS.
I am typing on a UK - layout keyboard right now, but with the SE/FI keymap set in the OS.
It could be confusing if you need to look at the keys to find a symbol, though.
For instance, the symbols for Shift-6 to Shift-0 are shifted one step to the right.
The German (DE) layout is almost exactly the same as Swedish for special symbols, but on the other hand, it has Z and Y swapped, and Ü printed on the Å key.