OK, here is an update. I must confess, I didn't do it myself but I called a professional detailer. He came to my house (complete with a very neat mobile detailing trailer which even included an awning to keep the car out of the sun)

Car was clayed and waxed. Result....UNBELIEVEABLE!!

Paintwork is now like new, smooth and shiny. A little expensive...maybe at $300 but 2 people spent 6 hours on the car which I think is good value.

The dirt that came out with the clay had to be seen to be believed. Car value must have increased by $1000 + with its new look paint.

I am very happy with the result and recommend either claying to anyone who needs to revitalize their paint.