In general, British English and American English are very similar, and either can be easily understood (except for some colloquial terms) by both American and British English speakers. There are, however, some key differences in spelling.
It should be noted that there are two different forms of British English (UK English) spellings accepted in academic manuscripts.
Oxford English (-iz endings)
Standard British English (-is endings)
The main difference between these two versions of UK English relates to whether -iz endings (e.g., apologize, apologized, apologizing), as in American English, or -is endings (e.g., apologise, apologised, apologising) are used. Notably, both versions of British English maintain all other spelling differences from American English. For instance, Oxford English and Standard British English have -ys (e.g., analyse), -re (e.g., centre, theatre) and -our (e.g., colour, labour) spellings in common.
Our services offer you the choice of editing in either British English or American English. If you choose British English, our editors will defer to the author as to whether -iz or -is endings are used. If both -iz and -is endings are used in the same manuscript, the editors will choose the ending that occurs more often in the text.
If you are not sure which to choose, please check the author guidelines of your intended journal. If they do not note a spelling preference, most journals allow either British English or American English (but not a mixture of the two), so you can choose whichever you usually use/prefer. As American English consistently uses -iz endings, it may be the safest choice if the journal provides no spelling preference in the author guidelines.