An item in a recent Courier mentioned that ethanol free petrol is now virtually unobtainable now, as BP Ultimate etc now contain 5% ethanol. I have been using Valvemaster Plus in my Vitesse 2 , but this does not combat the ethanol problem.
It looks as though Miller VSPe Power Plus is the answer ,,as this deals with ethanol, but this is not cheap
What's in your tank?