I've tried that, and assuming that fixing that issue will finally let me do my final year project the issue is that the supposedly overlapping geometry isn't overlapping. Or at least it shouldn't be. my first draft for this model had a thin sheet (0.2 mm) which I built to run exactly against the top layer of the metal struts, but when that failed I can to a similar conclusion and somewhat rebuilt my model. As a result I then had a sheet of the same thickness displaced for a small distance from the support structure. That also failed, so I tried to replace the thin sheet with a surface (which created its own issues, so I abandoned it). Just today I made a new one with a displacement of five millimeters (so a 5mm gap between it and the support structures) so I'm sure that there is no overlap. Now meshing is failing to either generate or update even when Fluent is not attached.
On the bright side, no more error message telling me of overlapping geometry, so that's nice, but I'm technically further away from a complete model now, which somewhat sours my better feelings about getting rid of an error message.
EDIT: New error message in the mesh editor:
Just getting the basic "Update failed for the Mesh component in Mesh.Error updating cell Mesh in system Mesh. View the messages in the Meshing editor for more details" in workbench