Came downstairs this morning to find the alarm light blinking on my Concentrator. Rang the emergency number at 0715 and a very nice lady told me to get on to my emergency cylinder, then took me through the power reset phase which made no difference.
She then said an engineer would be there within 4 hours. He came at 0905, with replacement concentrator, confirmed my old one was knackered, (white powder all underneath), and was away by 0915. Now back to normal.