Have you put the registration number into the ulez website to confirm its not compliant, my 260 is. EDIT THAT, now it isn't on this website which has a lot of adverts on it so I'm guessing it's not an official site https://ulez.co.uk/ulez-checker/. I'm guessing Mr Khan has possibly changed the emissions criteria but
On saying that i checked again on the transport for London Ulez which is the official website and it's compliant on that https://tfl.gov.uk/ulez