For the Dutch: British or American English?
You’re a Dutch native at home, able to write decent English. You learnt something akin to British English in school (lorry, kerb, crisps and the pub), but with all that American telly you’re being bombarded with, it’s all become truck, curb, chips and the bar. Modern Dutch culture is also telling you that this is the more international way to go, as Dutch borrows many words from American English instead of British English (i.e. ‘callcenter’ vs. ‘callcentre’).
The quick and dirty answer is use British English. The long answer is it always depends on the context.
Ask yourself these questions:
Who is your target audience?
Always consider your audience. Your choice of vocabulary is much more important than which spelling you use, but be consistent and don’t mix them up.
Are you writing English for a non-Dutch audience?
In this case, pick a spelling and simplify your vocabulary.
Do you plan to explain Dutch and/or European concepts?
Concepts such as housing, work and the government are very different from North America. In this case, I recommend using British English.
I use British spelling 98% of the time and American spelling 2% of the time. The latter is usually aimed at English-speaking North America, while the former is for Dutch companies expressing themselves in English for a non-Dutch, international audience. By the way, Canadians have their own spelling, but are used to reading American English, not British English.