I don't think there is anything in iBooks Author which is going to change your text automatically. If you do select all and set the language to British English, it should underline all the mistakes in red and you can fix them manually, or you could do find/replace for all the words you want to change.
Thanks for the idea of 'select all'.
It unfortunately did not pick up fueled as a mis-spelling, in the highlighted text for British, so this technique will have to be abandoned.
I will just have to read each word and then do the correction, highlight the red underlined word and convert to British.
Seems to work...
My wife is better at spotting errors so she sits with the iPad and suggests what to change on the Mac Book.
The -er in theatre etc are easy to pick up manually but the odd words that have one l rather than two are more difficult to spot.
Not that many words really to change manually but will check, check and double check.
That's really useful, but we should also take into account differing uses of punctuation, such as the Oxford (or serial) comma.
In some workflows, you could hold the text in InDesign, and use the GREP search and replace tool to create a script to do the horsework.
I tried 'find and replace all' but got some unwanted results......
I now use 'next' and then 'replace' ..... Much safer.
The tip about commas in the UK .....
"Portugal, Spain, and France" (with the serial comma) or as "Portugal, Spain and France" (without the serial comma)
We use the second option and I have never seen the former in publications in the UK.