I finally got it working. Agreed its an older version, we are a little limited due to Vendor older product.
The solution was :
(1) Update to Ubuntu kernel 5.4.0-150-generic
(2) sudo apt-get update
(3) sudo apt-get install linux-modules-extra-5.4.0-150-generic
Then I plugged in the USB GPS device, it found it, mounted /dev/ttyUSB0 and off it went.
Seems even though I was running 5.4.0-84-generic previously, it seems the -84 version it wasnt quite good enough to handle the USB serial properly.
Thanks everyone for your help.