I had to cross central London by car the other night. And pay ULEZ while the protests were on, it was kinda ironic.
I did se-up auto-pay earlier, but nothing happened (I didn't see the charge coming through on my card).
Also, drove south at 8pm, came back north at half past midnight... wondering if I will get charged twice or if there is a set amount of hours you can use with each charge.
It's 24 hrs a day, 7 days a week so I suspect you will have to pay twice. Friday, Saturday or Sunday, you have until midnight on Monday (or Tuesday if Monday is a bank holiday) to pay
Monday through Thursday, you have until midnight on the following day to pay.