Petrol is so expensive now what's the point about worrying about paying a couple of pence more. If you have paid good money to get the performance extra then make the most of it by putting in the good stuff.
When i first got my v5 i ran it on 95 and it ran like a bag of old nails. Stuck super in and it ran like a dream, better economy( not that it could be much worse!

) and better throttle response.
I have tried the new tesco momentum stuff. Initially I was quite impressed but over the last few months the running of the car has varied from tank to tank so consistency might be an issue. Running optimax now and its brilliant.