It was fine for a while, but then went completely unstable again. I phoned VM and was on the phone for over an hour today and the lady just came to a conclusion that she had exhausted all of her options (screen prompts I guess) and would need to refer it higher up the chain to someone who can analyse it (supposedly they will call back within 3 days) and they may replace the Hub 5.
There is a little bit of a pattern on the ping graphs and this only seems to be happening during hours where more people would be using the internet. It doesn't tend to drop out during the night as much, very strange!