I don’t know the UK regulations regarding labelling, here if it says E10, the pumps are posted, “may contain up to 10% ethanol.”
Shell V-Power is stated ethanol free, but after digging, & phoning,( senior product managers, not the local dealer), I was told by my preferred brand, that “Premium” contained no ethanol. The marinas here all sell 91 octane Premium, (at $1.60/L- I know, it’s cheap compared to your prices), in order to stay away from ethanol.
interstingly, this manager also told me they don’t actually order 3 different concoctions, they only receive 2, & that mid grade, (89 octane), is actually the same stuff as their Premium.
I changed out all the fuel lines in a ‘95 Seadoo, as the original grey lines were deteriorating inside, & I do run regular (E10), if I’m going to burn it right away. Later in the season, when the water gets colder, I stick with Premium, & no ethanol, as it might sit for a couple weeks.
I NEVER winter store any of my boats, lawn tractor, or other small engines with ethanol fuels. Premium, with stabilizer, I’ve never had any problems.
That said, I only have one 70’s vintage kicker, an Evinrude 6HP. I’m not sure what the float/internals are for that vintage, so I’ve only used ethanol free in it.
item last- when you store your engines for the winter, pull the fuel line off, then fog the engine as it runs dry. If you forget to run it dry, most carbs have a drain plug, pull that & drain residual fuel from the bowl.
These practices have kept my 22 year old chainsaw running like new.