Please excuse my ignorance, as I don't often go to London, and have little interest in it. Should mayor Ken not be voted back in (I know an election is coming up as the local TV news seems to keep going on about it), then would a new mayor not be able to scrap the congestion charge - perhaps not immediately (since there's that early exit penalty clause), but within their term of office.
If the London motorists are pissed off with Ken's charging, and proposed future charging, then vote for someone who would scrap it!