Unfortunatly that wasnt what i meant, i didnt realise there was a problem with waiting for coupling capacitors to charge. Although i suspect this almost solves what i dont understand. I can now narrow down what i dont get to a specific time: (time = 1 below)
time = 0 when power is first applied, (Vcc turns on) and no input trigger to the 1st 555 is supplied;
output of every 555 is low, the coupling capacitors are not charged so all the 555s except the 1st one are triggered.
If we dont want this then we must hold their resets low at circuit power on, for the time it takes to charge the coupling capacitors
i'm happy with time = 0
time = 1 Vcc is now on and all coupling capacitors are charged. There has still been no trigger provided to the 1st 555
the output of every 555 is low, the next 555s (ie all but the 1st 555) dont trigger because....... I dont understand why they not triggering!
time = 2 the 1st 555 recieves a trigger pulse and after time 1.1Rt1Ct1 (RtCt not shown on my diagram) the falling edge of the 1st 555s output triggers the 2nd 555 which after 1.1Rt2Ct2 triggers the 3rd 555 and so on and so fourth.
Thank you for your patience guys