I use BP Ultimate Unleaded, as there isn't a Shell garage any where near me. I don't really notice a gain in performance, with the engine only beaing a 1.6, but the engine runs soooo much better on the decent fuel. Get about 30-40 miles extra to a full tank as well. Definately worth the extra 11p a litre, as it 101.9p a litre where I live.
How much does everyone else pay??