Absolutely, if you have paid for it then you must be entitled to able to use it. But it depends on how it is charged for.I don't see that a Code Of Conduct would change anything - the majority don't waste energy so no change there - and the minority will just continue taking the view "I've paid for electric in the pitch fee so I'll use what I want"
But if a land lord/ site operator, or commercial business tries to sell power by the kWh unit of energy, they are bound by weights and measures, and their metering devices should verified in accordance with weights and measures regulations.