Your first stop should be the regional and national regulations for storage of gasoline in the quantities you want, in the country where you want to do it.
That will primarily be about safety and prevention of leakage, fire etc etc.
The National Aviation Authority will have regulations mostly concerned with quality of fuel being loaded into aircraft. Such as CAP 748, of course.
I don't know if EASA (through its Aerodrome and or Air Ops Regulations?) has anything to say about fuel storage and delivery, but if not they are probably thinking about it.