After many false starts and abandoned trials I finally have a circuit oscillating at exactly 300 Hz - apologies for the shaky camera work: -
https://www.youtube.com/watch?v=7doS...ature=youtu.be
Thanks to Radio Wrangler (David) who encouraged me down the route of using a Qantek QX14T50B4.915200B50TT oscillator.
Next step is to replace the HEF4060B with a 74HC4060.
After that it's looking at the output waveform on my 'scope and what I need in the circuit to drive an LED i.e. get my head round Tony Duell's comments in Post #6 above and all that stuff to do with "persistence"!
A general thanks to Forum members for their ongoing support ...