Morrisons E85 is being used widely in the Subaru scene, with great results and excellent power figures. Similar to people running meth mixes with the fuel.
US figures for 95 Octane is prob around 99, so with the meth mix your running a good mix. E85 is typically rated at around 110 Ron, however more importantly it's MON rating is higher than a "mixed" 110ron fuel, so will yield better results.
BTW, with regards to Thorney's findings back then, it wasn't just coincidence that Tesco's were the primary sponsor's of their race car...
Tesco's is primarily a 95ron fuel and mixed up to 99 using octane boosters, wheras the V-Power is actually a pure 98/9 ron fuel. Which is why you will probably get better MON ratings with the V-Power, better actual performance.
Best way to see how your car performs or see which fuel is best is check the MBT on each fuel.