thanks for all advice. radiators started spontaneously working again?! i know i should try to find out more about the fault but given current finances want to just apply the 'ostrich' method of problem solving.
Now, the boiler, timer, thermostat and upstairs circuit were all working, and all downstairs rads are bled and hot at the top. My reckoning is must be to do with the pump for the dowstairs circuit or an air bubble formed that then dissipated? any free online advice/suggestions.
and more importantly when will this damn weather end - somebody said its like narnia where its always winter and never christmas (spring).
My brother was a central heating engineer, he told me to turn the heating up to max. then turn off controls then bleed... are your radiators full of gunk? I think you can buy some stuff to clean them, if you can do it may help, then flush them if possible and put inhibitor in.