Hi Dave and welcome to the RH community.
Unfortunately there is no easy way to do this without manually renaming each topic via the Topic Properties. You could use a find and replace tool but be very careful to ensure that all instances of the file names are picked up (e.g. links, TOC references, Index references, etc.). It is so easy to make a mistake and end up with lots of broken links which is why I'd say the best method is to do this manually.
The RoboColum(n) @robocolumn Colum McAndrew
How about using a conditional build tag and basically tag each language based variant of a topic with for example an English language tag?
That way you could also use the tag to help control compiled output in different languages..