Last fill of the Interceptor was over the August Bank Holiday weekend, which was (I think) before the "official" start of using the the higher level of ethanol.
Last weekend I had 4 top-ups (30.5 litres total) in various parts of the country with the Classic 500 - can't say I noticed any difference in running after any of them. Fuel consumption appeared to be improving with increasing mileage - first top-up after 150 miles worked out at 91 mpg, with the average over the total 631 miles covered being 94 mpg.
The diesel car does seem to be less economical on B7 bio-diesel adulterated fuel than the previous version (B5 ?) - consistently around 2-3 mpg down on this time last year.
The MZ may be happy on low octane fuel, but not sure the rubber washers in the fuel tap & choke plunger will take kindly to ethanol & have read suggestions that some brass parts don't get along nicely either. Only time will tell.
Trouble is that you don't actually know what percentage is present - the 5 & 10 % figures quoted are maximum levels. Some E5 Premium fuel apparently has none at all