I tried to follow Wikipedia as closely as possible, but stupidly didn't keep my workings.
My starting point was the full list for Europe. From there I split off UK, then split off Scandanavia, then split off Southern Europe, then worked out a plausible split for the remaining western and eastern. For example, Czech fell into my eastern pile, but could have easily gone the other way...
I didn't even bother trying to bisect Africa or South America, as I couldn't find any evidence for such canonical bisections.
Now we're getting into semantics, but the point is, it says "including", and you can't "include" Finland and Iceland into Scandinavia. That would be like saying "North America (including Brazil and Chile)".
You could, however, say, Scandinavia PLUS Finland and Iceland - but that's not what OP wrote.
If you mean the British Isles (Ireland and the UK) then say the British Isles. UK is not shorthand for British Isles. Clue is in the name: United _Kingdom_ = monarchy, Ireland is a republic.
Looks like a fair solution, but the problem remains with the OP - I'm from Italy, if I see "Western Europe excl. Uk" I tick it, but then I would also need to tick "Southern Europe" ;)
Germany, France etc. will be turned-off or even insulted by the grouping and feel less impulse to represent than the named countries where a little nationalistic pride will be a motivator.
The reason for this turn-off is somewhat justified by your language - bother, pile, tedious etc. You must be American - jk!
My starting point was the full list for Europe. From there I split off UK, then split off Scandanavia, then split off Southern Europe, then worked out a plausible split for the remaining western and eastern. For example, Czech fell into my eastern pile, but could have easily gone the other way...
I didn't even bother trying to bisect Africa or South America, as I couldn't find any evidence for such canonical bisections.
Political geography is tedious.