I am driving into central London on Saturday morning for a one night stay and coming home Sunday afternoon. I originally booked train tickets but they have been canceled due to the strikes, this is the reason I have decided to drive. I have never driven into the congestion zone before, so am not sure what I need to do. I think I'll arrive after midday on Sat, so won't have to pay, but I will leave after midday on Sunday. How do I pay? Do I pay upfront or pay afterwards? Will I get notified that I have driven within the zone?