my 28cdi worcester boiler was working this morning?

my 28cdi worcester boiler was working this morning and has now stopped heating water and the rads are not heating either.. there is a red light flashing above the rad symbol and after following some basics maintenance steps on the cover, I have refilled the pressure/water to just above 1 which is slightly above the red indicator bar.... can't see anywhere that tells me what the pressure should read on a normal working boiler so unsure if I have filled it enough?? Hope someone can advise me.... Thanks