Ah, see I don't generally have that problem since we use mostly American English here. But there are some words that have a "u" in them, like colour (vs. color), favourite (vs. favorite), etc, and others that end in "re" like centre (vs. center).

Yes, I should have said it's a problem for non-Americans. It really can be a pain though. But apart from the spelling differences, you also will have a problem if a spellchecker doesn't recognise a band name or artiste name, like maybe the band Millenium, who spell it that way, even though it's incorrect in reality. Spell checkers would keep telling you this is spelled wrongly.

There's a lot spell checkers either miss, or get wrong, but then as I say there's also the grammar aspect of things, and the punctuation. Anyway, if I can help someone here I am, if not, well at least I offered.

Ah, well fortunately I have the intellectual capacity to ignore the little red line when it comes up in regards to UK V. US spelling.

You can download the plug-in for UK spellings (or anything else) here.

For Chrome users, there's an option to change spellchecking language (from US to UK english f.ex) in the program settings under "Under the Bonnet".