Well I have just returned home to find the photograph of the second offence waiting for me.
This time the picture is of the back of my car, same as before showing my registration number but the car pictured does not have a tow bar & mine was purchased with a tow bar fitted.
I have just contacted the dealer who is willing to confirm that my car was supplied with a tow bar fitted so I will be sending off a letter to the relevant Police force with a picture of the rear of my car showing the tow bar, no details filled in on the fine paperwork & a covering letter explaining that the car they have photographed is not mine.