I had to replace the water pump because it was leaking and did the thermostat at the same time because I was in there and I would regret it if it leaked some time down the track. Ever since then the fan has been operating when it did not before the work was done so I took a closer look at the problem over the weekend. The bottom radiator hose was not hot so it did not take a genius to work out that there was a circulation problem but the question was why. I got hold of a vacuum bleeder and had another go at bleeding the system with no success but no go on that so the next question was whether the thermostat was plugged in and working and that is impossible without pulling the inlet manifold off to have a look and after doing that we found it was connected anyway. The long and short of it all is after a chat with our dealer it turns out that VW released a software update for replacement thermostats last week specifically for this problem. Four hours down the slot because we did not talk to the right person!