Might be time to get serious. If your vehicle is registered as a commercial, is older than 2002 and is likely to travel virtually anywhere inside the M25 there's a massive fine if you don't comply. And you can't dodge as there are cameras on every road. Seems to affect pickups and commercials, not "car-type" models. Example at http://www.tfl.gov.uk/assets/downloads/roadusers/lez/LEZ/case-study-pre-euro-land-rover.pdf