Thanks for taking a look and I'm really sorry for having wasted your time...
...I had allowed C&C RA 3 and Revora in my firewall yet it turns out it is the firewall that's the problem. I really hate doing it but I disabled my firewall just in case and it worked, I logged in and was able to browse game lobbies. Now I have to identify the component that doesn't have a rule set up for it to allow it but at least now I know where the problem lies. I won't be able to get to that for a couple of weeks (going to visit family) but when I'm back I'll poke about and see what I can find.
Thanks again for your efforts.
Cheers, Mike...