I uninstalled and re-installed, during the first install I'd not allowed Avast to add itself to the registry as a startup program. I have a feeling this is why I didn't have the blue 'a'. I have that now
So, this all makes a lot more sense now. I added the string 'protectx.exe' to the exclusions, under advanced, then tried to start it, it still got detected and killed, but I've found that by pausing the service I can manually start it and it's all good. However now that I see what's going on, it looks like Avast provides similar functionality, in that it monitors incoming network connections. Will it alert on attempted connections (attempts to telnet, ssh, or ftp into my computer)?
The other thing that protectx has provided me is that it absolutely blocks anything being written to the registry (pop-up asking if I want to allow the key string to be written), is this in the Home version of Avast? If so I can retire protectx.
Thanks for all you help and patience.