I have resolved the issue with the marriage data not being displayed.
I use PAF (Personal Ancestral File) for my data storage and to make my life easy I was doing a Lefever restricted export to Gedcom and then converting that to a CSV file to then display the data on this site. It seems that when you export restricted name data from PAF it doesn’t export the family data if the male spouse is not included in the export. This seems to be the only shortcoming that I have found with PAF so far, I will check the documentation to see if it is something that I am doing with the restricted export.
I therefore did a full Gedcom export and then edited the file to remove the non-Lefever entries from it and the updated data including the marriage details is now displayed on the Lefever-GB page.
Now back to doing some more transcribing.