I had 50 miles remaining I think, wanted to fill with "cheap" fuel (less than £1.35 a litre). I've taken it to 15 miles once before- and I guess there is a safety factor built in!
It was "nearly 700 miles" IF I had run it dry
I don't think the tank is vented, I read about this on tdiclub. There's no button thingy to press like I had on a Citroen.
Need to find the time to do some rear wheel fairings now!