There are a few different reasons you might be experiencing buffering while streaming Foxtel.
First, it might be that your speeds are too slow to keep up with all the data that’s being sent. To find out, you can run a speed test; users with download speeds of less than 5 Mbps will almost certainly experience buffering with HD video. You may notice improvements if you reduce the video quality or pause other data-intensive apps (P2P clients, for instance) in the meantime.
It’s also worth noting that every VPN reduces your speeds to some degree. You should expect to see around a 30% reduction, but if it’s any more than that, you might want to try using a server that’s closer to your actual location. Finally, you could try a server with a lower load since the more users on the same server, the slower their speeds will be.