I bet your csv file uses quote characters! You cannot have any of that. Your file must be perfect.

Your file contents must be exactly seven characters: GBP/AUD

No quotes, no commas, no newline characters. It must be pure.

If you right-click on the file and click Properties, the file size must be seven bytes.

From R, one very good way to write the file would be to use the sink() method:
https://stackoverflow.com/a/2471806