I from the US, just learned about these today, and had a chuckle.
an essex girl was driving down the A13 when her car phone rang. it was her boyfriend, urgently warning her “treacle, i just heard on the news that theres a car going the wrong way on the A13. please be careful!” “its not just one car!” said the essex girl “theres hundreds of them!”
Not from the UK - why is it Essex in particular?
I would say Essex is stereotyped as being relatively affluent but lacking class, and is often a source of jokes.
I tried to find a succinct explanation but couldn’t so if you want a long read