Well…the moral of this story is don’t let your 3 year old grandson near any electronic projects!! Hugo (for it was he) gleefully held the flashing Xmas tree in his hand and, without me realising, had proceeded to wiggle one of the capacitors so much that it had broken the track it was soldered to! All fixed now and flashing away merrily (and out of reach of the grandchildren!!) Thanks for all the advice.
Incidentally I am fascinated how this circuit, which on the face of it it two push-push circuits together, manages to change the flashing sequence without the use of an IC in the circuit - clever stuff…!!
All good wishes,