I would have asked at the outset how often the billing was. Foxes bill every quarter.
I installed a standard elec meter (£12 from QVS Direct) in to the shore supply cable on my own boat.
If you want to control your use. Install a coin meter (About £30 upwards on Ebay), I have done this
on a number of boats who's owners were on fixed incomes. They put in a few more coins when they
have spare cash, building up credit and they know money is there for the bill.
I do heat the water using elec, My bill is only £25 per quarter
As for the bill, you have used the elec, So you will have to pay, Ask the owner if you can pay by installments.
If it does go to bench, The marina owner will have to explain his haphazzed billing methods.
Firesprite
Middle Levels