Sorry but it's highly suspect to be spelling the same word multiple different ways across paragraphs. You switch between using centre/center or utilization/utilisation? It is a very weird mistake to make for a human.
I mix British and American English all the time. Subconsciously I type in British English but since I work in American English, my spell checkers are usually configured for en-US and that usually means a weird mix of half and half by the time I've fixed the red squiggles I notice.