Spellings should be checked against the Oxford English Dictionary. The only exception is that we use the “-ise” word ending and not “-ize”. Always use the spellchecker before submitting your content, and make sure that the spellchecker is set to UK rather than US spellings.
Always use the facility in your CMS, if possible. Your work must always be proofread too, as correctly spelt words can be used in the wrong context.
You have to reap what you sew