I think probably a bit pointless. Your vehicle only has to be Euro 4 to avoid it, I think? Which is something like 05 plates. I don't think it particularly hits the poorest hardest, you can pick up and 05/15/06 car for a couple of hundred? They should maybe have had a small scale scrappage scheme I guess, requiring proof that you live / work in London, giving say £1000 for 02 - 05 plates. You can definitely get a decent enough newer car than that for £1000
.
But yeah, most family / individual vehicles aren't affected anyway, surely? More likely to affect vans and delivery trucks, I guess.