What does F43 error message mean on Glow Worm 24/30cx?

Boiler got serviced last November then last night it stopped working. At first it was showing F1 and F4. Then this turned to F43. According to manual, this is generic fault whereas the first two are ignition fault. Manual doesnt say how to fix both so we need to call gas man but even to come take a look, we are going to be charged. Just wondering any advice here.