When we moved in here and the NBN tech came out to connect us he stated that we could only have ONE connection, all others (3 of 4) had to be disconnected. He did this but we still had some teething issues in the first couple of months. The same tech came back and ran through all the connections the ensure there was only 1 that remained. Kept it simple and placed connection in same room as computer. Less problems after that but these were related to ISP not NBN. Have now changed provider and have much much better service.
You could try running your Foxtel with a pass through powerline adapter. We have one that runs SWMBOs Fetch Box and works quite well.

