Just get a compliant car so you don’t have to worry about where and when to pay
Eg. "No left turn on school days, except permit holders, except for access".
Whose school days? What kind of permit? Where do I have to be going for it to count as "access"? Do I need documentary evidence of the access, for example a receipt from a shop down that road? Left turns may not be allowed, but are u-turns allowed? How about driving 50m past, u-turning, then turning right?
Am I allowed to stop the car to look up the school dates on my phone? Or would I then be stopping in a no stopping zone?
Driving anywhere unfamiliar around London as a non-taxi-driver seems fraught with fines despite a driver's honest best efforts to stick to the rules.
There are sometimes signs which only apply at school times, they say things like "School 20 when lights show" - I think I've seen them in Scotland