Multiple times I have seen people 'correcting' British English words and terms in a question to their American equivalent. Words like colour are changed to color and customisation is changed to customization. No matter how big the US is, British English is still the world language and the main language on the interweb. I get that they automatically use their own grammar in their own questions, but editing other people's questions to fit their grammar seems a bit odd to me. Why do people feel the need to do that?
To be quite honest, these types of edits should not be approved. To me it boils down to a term called "local color" (or local colour in your case, @Bart :o). While Stack Exchange is (for the most part) supposed to happen in English, the rules don't dictate "American" or "British" or "Whathaveyou" English. As long as we can read it, there shouldn't be an issue with you (or anyone) using "tyre" instead of "tire", or even "bonnet" for "hood". As long as the version used can be read and understood, it should not be changed.
A bit in people's defense, this is more of a reactionary change than it is to try and mess with someone (in the vast majority of the cases, anyway). I'd bet most people don't even realize they are doing it. They see something, which in their mind, is spelled wrong, and find the need to fix it. They don't give thought to where the other person is from or what have you. It was a mental bridge which I had to cross at one time, but I do think about it now before I arbitrarily just change something.
There is one caveat and that has to do with tagging. We should not have multiple tags for the same thing. There was a tag war which occurred a while back because of the use of tyre instead of tire. While both are understood to be the same thing, the use of two different tags for the same thing muddles the waters. Because of this, it was decided to use the American version of tire with tyre being a synonym. While this didn't sit well with a few people, it was done in an effort to conform to one standard and one tag so stuff could be more easily found. It has nothing to do with which is right or wrong, because neither is.
If I see it happening, I will rollback the edit. If you see it happening to your posts, I'd suggest you do the same.
I would consider localization-related edits to be too minor to approve, since they don't really add much value.
That said, it may be that the edits are coming from individuals who don't realize that there is more than one way to spell "customise", so I wouldn't make a big deal out of it.
If it bothers you and the edit is made to your own post, my suggestion would be to roll back the edit and not think twice about it.