think mr singh in his 1.1 (and a lot of the fortwo owners) use v-power in their cars and they get better mpg overall.
if you do decide to go for a higher octane then shell is your best bet (its not actually any more expensive than the supermarket stuff)
JJ
you are correct JJ.... my 1.1 has run on V-Power since i bought it with the odd fill of normal fuel and overall it works out cheaper than the normal stuff.
1)Shell V-Power Nitro+ is only 8p more than Shell Fuel Saver
2)you get double points of you use V-Power
3)you go further on a tank if filled with V-Power
4)the power delivery is MUCH smoother e.g. at 4000 rpm in 1st there is a noticable step when the VVT changes on normal fuel and its hardly noticable when running on V-Power (a hire car isnt the fastest car in the world if you drive like me).
5)if you opt for money off fuel vouchers then it works out even cheaper.