About the situation in Belgium, I would like to point out that your statement “Belgians generally understand their neighbours’ language” is not correct: all Belgians understand the language written in the Netherlands and France, as well as the spoken languages, provided the regional accent is not too strong. The differences in word usage you pointed out do not prevent understanding.

I understand that you are not out play down the importance of regional languages such as Welsh, but I would like to add that even a multinational business might want to consider translating into these. Many small languages mean a lot to their speakers emotionally and they are likely to pay more attention if you talk to them in their preferred language – just like Belgian French speakers prefer Belgian French, even if they don’t always insist on it.

And just one more thing: the way you’ve used the term Gaelic would suggest that it is a single language with two variants, Scottish and Irish. This would be a misunderstanding. The general consensus is that these are two separate but related languages, with separate ISO codes (‘gd’ and ‘ga’ respectively), and I can confirm from my own experience that they are not mutually comprehensible: I speak one fluently but understand next to nothing of the other.