Thanks for your help again Jumpy. I have tried to follow up the idea of using additional connection points, but I am now hopelessly out of my depth unfortunately.
It is frustrating that MS have implemented the built in label in a way that can’t be copied. Perhaps they have used "...some built in mystery algorithm..." as they were unable to define it in the shape sheets either.
When I got my company to pay hundreds of pounds for me to upgrade to Visio 2010 pro I thought I would at last be able to draw network diagrams with it, I didn’t dream how incredibly difficult it would be to create a connector with labels that behaves in a useful way.
It seems that a lot of people use diagraming tools to document what they already have laid out in their head, so the layout doesn’t change that much during the construction of the diagram. My brain doesn’t work like that & I expect to add each device & connector one by one. This always leads to rearranging the diagram lots of times, which is why for me it is essential for the labels to move dynamically with the connector, but not get repositioned without need. (e.g. if the left end of the line changes then the right end label should not move).
If anyone is familiar with the now defunct NetViz product, its connector labels worked well.
I am beginning to suspect that a Visio solution is not practical or I guess I would have found some examples on line by now. I can tell from my research that this question has been asked plenty of times before so it would just seem that no one has managed to find a solution.
Thanks for listening to my ramblings.