Thanks guys.
I got the wife to take it for a 1.5hr drive yesterday, so we're keeping an eye on it. Also last night I took the car for a drive but once the engin heated up, I kept it up in the rev range (for a diesel) at 2500-3000rpm in manual mode. I'm hoping that this was enough load on the engine to generate the heat to trigger a regen and burn out whatever it thinks is in there.

We're keeping an eye on it and will see how it goes. I also found on the Ross Tech website how to trigger an "emergency DPF regen" via VCDS. So if this happens again in the near future, I'll do that.

Yep the car is still well within the warranty period. It's only 2.5yrs old (with a 5yr warranty). My wife did mention it at the last service she recently had (about 3 weeks ago), but they said the fan running is normal. I think they may have misunderstood - as we get it's normal...but not normal to run for extended periods, or when the car hasn't even been used.

Out of interest - do any of you know how often the DPF will regenerate? Is it something that only happens once in a while (or takes a while to build up before a regen is triggered?), or is it actually something that can happen everytime the car is driven if conditions are right?