I think there are two main issues with E10. One is the compatibility issue which is to say that for any particular vehicle will the fueling system be affected negatively by the corrosive nature of E10 - fuel pipes, seals and the like. You can easily check that out here:
https://www.gov.uk/check-vehicle-e10-petrol
The other is that you are likely to get less MPG using E10 as it's slightly less energy dense. Oh, and E10 will absorb more water vapour so if the vehicle is likely to lie up unused for periods of time I'd be using E5 to lessen the likelyhood of water collecting in the bottom of the tank (you can buy fuel conditioners which combat this). For this reason I use E5 in my old Horticultural machines.
For better or worse we tend to fill up at either Morrisons or Asda with E10 which we started using in both the cars as it was introduced. Can't really say I've noticed any significant difference in the way either vehicle drives - 2010 Panda 1.2 Eco Dynamic and 2016 Ibiza 1.0 litre 3 cylinder turbo ecomotive.
I would not expect the 60hp FIRE engine in the Panda to be able to make any better use of a higher octane fuel than it does of the 95 RON E10 but I've sometimes wondered if the Ibiza with it's turbo and sophisticated ignition system - needed to control knock with the use of the turbo - might produce more power and better fuel consumption on 97/98 RON E5. So, back in the spring when we went on our "Devon Odyssey" I let her run out to nearly empty just prior to leaving and filled her to the second click with Shell V power E5. A tankful just gets us there so next day I filled up to the second click off (my usual procedure) and worked out the consumption. Over the last 5 times we've done this journey in this car she's consistently returned between 58.5 and 60 Miles Per Gallon for the whole journey. I was slightly disappointed to find she was right on the 60mpg this time - measured not by the onboard computer (although, on longer journeys it's really very accurate) but from full tank (2 clicks on a level forecourt in Edinburgh) to full tank (2 clicks on a level forecourt at Tesco in Barnstaple). So, in my experience and as a result of my unscientific observation, The considerably more expensive higher octane E5 produced the same driving dynamic and fuel consumption as the 95 RON supermarket fuel. Which is not to say that the superior additive package in the higher octane fuel maybe benefited the engine in other ways which the E10 couldn't?