thank you d12dozr. Your skp works fine (of course) so now I can see where I am going wrong.
[Alan your signature reminds me that I proposed to my wife at Formby point many years ago.]
Still unsure what the two lines do when you draw them after clicking a start point with the mirror tool selected. I have played around with it for ages but can't seem to work out the rules of it.
thanks again (much appreciated)