Tesco have been doing this for some time. You are allowed to do up to a 5% blend according to the regulation the fuel is to (EN220 or something? It says its on the pump)

Its a BAD idea overall as there is 30% less energy in enthanol per liter, so really your paying the same amount of cash for 98.5% the energy that you think you are. Its why supermarket fuel is cheaper.

JAmes.