There are barely any of those. Even 19-year-old cars still qualify for ULEZ exemption as do really old beaters so only cars that are between 20 and 40 years old have to avoid the zone or pay.
It was a bit of a pain for me as I ended up swapping my 31 year old car for a 12 year old car but I'd rather have clean air and the 31 year old was getting a bit rusty anyway.
The change in air quality has made a big difference for me, I've been central for ~18 years and was thinking of moving out because the pollution was making my eyes sting all the time but it's much better now. Partly ULEZ and partly other stuff like the taxis going electric and the busses getting better engines.