Central Heating Malfunction!

I wondered why the house was cold when I got up this morning! The hot water side of the boiler was working but the central heating was not working. 3C outside. :-(  I put a fan heater on here in the study, managed to get the temp up to 18C when I took this photo. My sitting room temp is the extra!!!! British Gas informed and hopefully the engineer will be here before 6pm. Glad I have a maintenance agreement with them!