The manual in the latest BBs say no more than 10% ethanol. I have run mine for most of the last 18,000km on E10 95 & consistently got 17.5km/L.
Recently (last 4 fills), due to where I was when I had to fill it, I tried BP 98 RON (no ethanol). When I previously used various fuels, my mileage stayed consistent at 17.5km/L, (mostly Shell standard unleaded 91, E10 95 & V-Power 98), but I have now found that my usage has gone from 17.5km/L to 19.3km/L for the same commuting that I always do. Will try on the Shell V-Power again, when they actually have some. Refinery problems mean they have been out of stock here for about the last month!