Thank-you.
I think it will have to wait to see what happens. Gosh if my speedo underreads, then I could have been going as fast as 60MPH! I have never heard of overreading speedometers but i suppose it's possible. I have also heard it said that 'margin of errors' are usually in the driver's favour, but that can't be always the case as this website wouldn't exist!
The guide at the side marks me as a Newbie, however I was a member of the predecessor site, Pepipoo for many years, now switched off.