V6 110 miles return EGD to Manc on BP Ultimate: 44.7mpg
V6 110 miles return EGD to Manc on BP Standard: 39.1mpg
Tubby 110 miles return EGD to Manc on BP Ultimate: 43.0mpg
Tubby 110 miles return EGD to Manc on BP Standard: 42.5mpg
Tubby 110 miles return EGD to Manc on Asda Standard: ~35mpg
(remember the above numbers are repeatable to +/- 0.1mpg)
V6 10 miles return to work (very urban) on BP Ultimate: ~22mpg
V6 10 miles return to work (very urban) on BP Standard: ~19mpg
Tubby 10 miles return to work (very urban) on BP Standard: ~14mpg
(fairly wide variance in these numbers to +/- 2mpg)
Not bad eh? Looks like BP Ultimate's actually better value than the standard stuff in this car, PLUS I can get better economy than the old tubby... as long as i'm not red-lining it in 5th...

Wouldn't mind comparing all the fuels again, but I just don't do the repeatable journeys now. I may update this next time I know I'm going up to manc and can pull into a petrol station on fumes...