Thanks CRX - not too bothered with the value but nice to know a bit more about it.
It was produced between 1958 - 1964, going by the pictures I would put the value at the low end of my previous estimate.
The Mk 1 was made between 1924 - 1964, and they were sold in great numbers, so unfortunately you can't retire just yet!
Thanks CRX - not too bothered with the value but nice to know a bit more about it.