I've got it working now. Unfortunately, I made many changes before retrying YOU, so i don't know exactly what enabled it to work!
Anyway, here's what I did:
Disabled the firewall on the local machine.
Went to Control Centre, Network Services, Proxy and set the proxy to http://x.x.x.x:8080
and stuck in my authentication settings in the format; domain\user, password.
Went to ControlCentre, YaST Modules, Internet and Network, Proxy and stuck in my addresses and credentials again, and ticked off the box; 'Use Persistant Connection to Proxy'.
The online update worked fine after this, and my SAMBA client now works.
Hopefully, this is all you will need to do, as the rest of my changes happened to involve a complete custom re-install from scratch.....