I’ve driven into Bath a fair few times in the past year, and there’s plenty of signs – both CAZ ahead and at the bondaries. I did accidentally enter once (ironically, I needed fuel but didn’t realise the Sainsbury’s entrance was just inside the perimeter), but it was obvious where the boundary was once I reached it so just paid the same day.
It only targets pre-Euro 6 diesel and pre-Euro 4 petrol vehicles, so seems a good way to improve the terrible air quality in inner city areas. General taxation is too general – this is to target the particular problem of air quality, not the general problem of CO2e.
It’s worrying that you can miss all of the signs and cameras – what else aren’t you seeing?