I've had a look through the archives and dug out the figures from a couple of Top Gear style tests I did years ago. It's a bit different in mine to you guys since in the pre-facelift you don't have the trip computer telling you many miles to go etc. But..
1) The first I stuck to 2000 rpm from a full tank for just general driving around. The petrol light came on after 313 miles.
2) I did the same again at 2500 rpm. This time I just got to 306 miles.
3) After a trip down to Portsmouth, I filled up at the Shell Victory on the edge of the city before driving back to Whitehaven - a distance of 375 miles. I then cruised up at pretty much a constant 60 on the motorways and DC's all the way back. The petrol light came on bang on 6 miles form home, so 369 miles.
And... what you have to remember is the petrol light generally comes on with 50 miles to go, so the last one does show it's possible to break the 400 mile mark on a full tank.
