Many many thanks to everyone for all the advice offered. I very much appreciate the support.

I have finally found success!!!
I just need some clear skies and a good target.

I though it would be worth posting with my findings.
After update to StellarMate 1.4.0 I still had no success with the usb-serial connection. In addition, the update seems to have broken the web manager.
So I'm back to 1.3.5 again which is working well.
I have a new USB-Serial cable, this time with a genuine FTDI chip, and this has worked "out of the box". Since it has a different vendor/product ID from my GPS then I don't even have to use the Serial assistant or any UDEV rules.
It would seem that the CP210x chip does not play well with StellarMate.

Hope this info is useful for others.

Chris

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