Vaillant 837 heating won't come on status s.30 even though it's FREEZING!!?

Please please help. I've had some work on my electrics today and now the power's back on but my heating won't come on. The digital display shows S.30 'no heating requirement' but I'm freezing. The display reckons the house temp is 60 but it can't be. I've tried turning on and off, pressing reset switch, I've read the manual back to front but it just won't spark up. I have a terrrible cold and am 6 months pregnant, I'm desperate for a but of heat and would appreciate ANY advice - thank you so much