The government-provided information on E10 and E5 petrol here - www.gov.uk/guidance/e10-petrol-explained - first published in 2021 states that owners of vehicles that are not compatible with E10 or classic cars should continue to use E5 "which will remain available in the 'super' grade". As premium petrols provide E5 for those vehicles that need it as well as a higher octane fuel for performance cars, we would expect this to remain available for some years to come.