Sub39h, do you not remember the massive problems a few years back with supermarket fuel causing engine failures?? It was all over the news.
Ethanol enables petrol to absorb water, slowly via the atmosphere, but more damagingly when it's collected in the containers which store the fuel due to bad management of them (allowing rainwater in etc). Petrol alone does not absorb water.
When you mix it in the volumes the supermarkets do (typically 10%), there's a higher risk they'll put a bit too much in, causing it to eat materials. Also, the more ethanol there is, the quicker the effect of water absorption happens, so if stored badly or too long, the risk of water related engine failure is greater.
V-Power uses ethanol blend, however in smaller amounts and with their own additives to boost the octane. This is 5% maximum content.
Ethanol in fuel is actually a brilliant thing, and turbo cars love it - However I don't trust people buying and selling at the bottom end of the market with anything, not just fuel. I work for a bank, I've no interest in Shell's profits or business.
I don't doubt that Tesco fuel is actually better, but I won't buy it. Just my opinion and in no way an instruction to others. You're all adults, investigate it for yourselves and make your own minds up.