I'm working on the master config...
One thing it needs is the (domain name and) port number where buildbot's own http server will be visible. Default is 8010. I guess it just needs to be open to the WAN and that's it.

I think 8010 and 10012 are not filtered on that network.
 
So, we have an 'alpha version' of the master config up and running
http://128.238.56.50:8010/
Tomorrow i'll shut it down (first i wish to see how the scheduler behaves) and continue configuring... need to give meaningful names to slaves, check scheduling, source access + change tracking and finally the actual build processes.

Andras