I just came across a comment where someone was annoyed at having to use American spellings when programming due to the fact that many libraries use American spelling.
I can sympathise with not wanting to spell colour as color, but I was less sympathetic when he complained about having to use the spelling Globalization in C# libraries.
As I understand it, the use of the spellings -ise and -isation are considered a UK thing, and are not used (or are less common) in the US. Nevertheless, the converse is not true: that is, the spellings -ize and -ization are not confined to the US, but are in use in the UK as well. I'm not even sure whether the -s- spellings have a majority in the UK.
Besides, if they want to use "proper" and "traditional" spellings rather than "new-fangled" and "alternative" ones, then they should be using -z- anyway; to the best of my knowledge, that morpheme comes from Greek -ίζω via Latin -iz-, so the spelling with -z- is more justified etymologically. (An exception is analyse, which had an -s- [well, a sigma] in the original Ancient Greek; the spelling analyze is, I suppose, by analogy with verbs in -ize.) For that matter, they should also call the chemical element aluminum, which was its official name; the spelling aluminium is a later modification.
As for me, I prefer the spellings colour, globalisation, aluminium, but more because it's what I grew up with than because I think that all those spellings are "more original" or "the only proper British spelling".