The use of stand pipes is not ordered by the water companies and this is partly responsible for illegal usage.
Thames Water - you pay £150.00 for up to 10m3 per day, over a month period. This can be paid up front and on a card.
Wessex Water - you have to go to their offices and pay to hire a metered standpipe and then pay for the usage per M3
If you are working 50 miles away from their office it is a nightmare to go and collect and then take back.
If you are caught using hydrants illegally you will be right royally shafted and the fine can be up to £5000.00 and immediate taking of your kit.
Be careful
Rob