New E10 fuel is out, Gov website says our S2’s are fine to run it.
Has anyone noticed any difference to economy, general running, performance? Is it safe to leave in the fuel system for long periods, i.e. winter storage?
Heard reports the ethanol eats rubber fuel lines on older cars!
You guys running aftermarket ECU’s having to retune?
Shouldn’t be needed, it’s not altering the octane rating of the fuel. US have been on E10 for yonks I believe, and it’s a bit more popular on their summer cars to leave them parked up with some sort of fuel stabiliser added to the tank. You know the bottles of stuff we’ve considered snakeoil for years 
That said, I think most people running aftermarket ECU’s are running super anyway, so the E10 change isn’t relevant.
Useful info here from FBHVC about E10 and other fuel-related matters:
Probably the best and most sensible article I’ve seen so far.