As advised by Umberto a complete uninstall followed by the full install of v4.51. As I said when I updated to 4.4 it didn't work properly. Even though the uninstaller said it was uninstalling v4.4 Umberto found many files relating to V4.3 so a complete uninstall was the safest way.
Steve
After the client 4.3 -> 4.5 update, in the course of freshening up a few of the add-ons, and as a result stopping/restarting P3D v4.5, the signage on the default jetways is now BACK. I didn't do anything else. I have read that a P3D update can take a few restarts to get completely set in, maybe that was it, don't know.
A complete fresh reinstall is a rather large undertaking, with all the add-ons and customizations I have. I think I would just put up with the jetway issue, if that was the only solution, or better to just backgrade GSX, if that was even possible.
In any case, I'm good for now, will report back if I continue to have trouble.
* Orest