Right.... and ill put this in laymens terms.
The Higher the octane level, the higher the compression needed to Ignite the fuel. Meaning, the fuel is less likley to ignite on the upstroke of the piston, thus resulting in pre detination, or engine knock etc. High octane fuel has very very little effect on BHP. If your are feeling a difference with it, then im sorry to say, but that is just a placibo, or as Bazzer1955 stated his VRS runs like crap on it, I would suggest running Colder Plugs in your car, as like most VRS its probably had an "ebay chip tune"
The octane rating of E10 is 95 ron, exactly the same as the "old regular unleaded".
Only downsides to ethenol is its ability to eat rubber. I have an a4 with a 1.8t and runs on c85 race fuel, which has no petrol in it at all. 77% Ethenol. and 33% oxygenates. I have to change injector seals every 6 months or so, or I start to get that lovely Corn juice smell inside the car. Octane rating has nothing to do with BHP.
Personaly I have absolutly no worries about having 10% ethenol in the fuel. Its better for the enviroment. And most of the Horror stories of "I have a mate, who knows a bloke, who spoke to a bloke in a pub, that he used E10, and all the rubber hoses in his car evaporated" they are warning people off of E10 in cars older than 2000, becuase they have rubber fuel lines and seals that are over 20 years old, and the sudden change of chemicals may require them to be replaced.