Greenergy supply Tesco 99 RON (now called Momentum). Quality certificates are here
http://www.greenergy.com/Buying/fuel_certificates.html
Bioethanol is used to increase the RON rating.
In my view nothing wrong with the fuel, I use it in my car which is now at 137k miles. Have used Tesco 99 almost exclusively since I got the car when it had done just 32k miles.