(apologies for double posts for original comment)
As I understand it, fast charging 50kW facilities such as at motorway service stations provide electricity at a specific rate. They’re clever enough to know once a vehicle is fully charged and there’s then an ‘Overstay Fee’ that automatically kicks in of between £5 and £10 per hour. The onus is on the car owner to unhook from the charge unit as soon as they have enough for them to continue on their journey.
For an overnight 3.7kW charge that methodology wouldn’t apply as even an overnight charge in cold weather may not provide a full recharge. But for an on-street residential charging bay what is to prevent an owner of an EV just parking in there and not even connecting in the power lead? Maybe they got fully charged at work and don’t need a top-up and are just using the EV bay outside their home as a convenient spot to park.. how do you get turnover in that bay if the approved sign doesn’t provide a variation for a ‘Maximum stay’ period?