Worcester Greenstar CDi Boiler will not light?

Worcester Greenstar 40 CDi Conventional Boiler GC number 41-311-72 will not light. New boiler last year, OK until returned from holiday during which time CH left running on low T/stat setting (For info. Elect supply power cut at some time -clocks now wrong time). Fan runs, clicking sound from elex panel about once a second. Nothing (no flashes or flames) visible through window at ignition electrode & flame sense electrode assy. No burner on light (green lamp). Gap at electrodes is about 8mm. Today is Sunday, Xmas eve tomorrow! Help!