It's fairly common for us to use "-ise" instead of "-ize", but having now looked at Wikipedia on the subject, it appears that I incorrectly thought of "-ize" as an Americanism. The "-ize" suffix predates "-ise" - it comes from ancient Greek/Latin whereas "-ise" comes from French.
It would be a good habit to check (for example on the Wiktionary – I have a Chrome search keyword dedicated to that) because those are not the only differences.
In British English "judgment" without the 'e' is generally only used for talking about judicial rulings, whereas most other uses of the word contain the 'e'.
