No, the solution is to increase the charge until congestion is at the desired level. That's the whole point of charging for access: if you are supplying more than you'd like to, charge more until you're supplying just what you want.
If you only want a certain number of cars driving in the city with good reason, then charge the amount which gives you that number.
Perhaps the reason London hasn't set the prices correctly, is that they want maximum revenue instead of a truly limited supply.
