ALAW, I've also looked at this, having looked at several articles and the car care nut & The Fuel Reviewer (YouTube) petrol cleaner/additives is not needed, instead, use premium fuel whenever you can with as little ethanol in as possible. My preferences are as follows...
ETH means ethanol
1 Esso E10 6% eth, E5 0%
2 BP E10 5% eth, E5 0%
3 Shell E10 7.5% eth, E5 2.5% eth.
4 Gulf E10 2.5% eth, E5 0% eth
Just use premium fuel as often as you can (every fill-up or maybe once in 3 fillups)
MOT