So what arrangements had you made for the security of this valuable cargo at your destination - and what arrangements for parking where you were to unload? It's getting even less likely you had 'never heard' of the congestion charge since this must have been a business trip.
If you need the vehicle because it's carrying goods you should be pleased about the congestion charge making travelling around the centre easier - I certainly am as I too use a commercial vehicle in central London - just not a car for transporting only myself.
BTW, I rarely use the tube. I prefer the overground or buses.
Good - we probably wouldn't have understood you anyway.