Took a bit of finding (had to use a google search targeted on the Unitronics web site, as site itself does not seem to have a usable search function ?? ).
For future reference https://unitronicsplc.com/Download/SoftwareUtilities/
It does the job, thanks, although the converter does not seem to be able to access or output to anywhere but the /onedrive/documents folder on my Windows 10 machine. You can select different directories, but it ignores your selection and drops back to that default. Probably a Windows 10 "thing".