I have been pondering this and doing some reading.
Ethanol does absorb water, but I personally am not too concerned as there is little opportunity for it to do so. The tanks on our cars are sealed and have a carbon canister to capture vapours so the only ingress can be of air, through the tip over valve as the tank drains. At most I would say 80 litres of air could enter on each cycle. If it was at 50% humidity and 30 deg C, that air would contain 11 grams of air per kilogram and the 80 litres of air admitted would have 0.011 grams of water in it. In volume terms, that is 0.011 millilitres. If the tank had an open breather, then I would be more worried as vapour pressure would drive in more moisture once it had been absorbed.
Ethanol’s corrosive properties on things like solder on carburettor floats and certain rubbers would be a concern, but in the case of later cars and ours particularly, this isn’t an issue.
I am concerned about separation of ethanol from the petrol in storage, so I will be using a stabiliser when storing my car.