Returned from 5 days away to find boiler as dead as a dodo. Mother in law swears it was workign 2 days ago as she lowered thermostat and carpenter in fitting new doors had hot water yesterday. However i get back today and no heating or hot water. Chek boiler and no lights at all, nothing. Digital timer ok (battery operated) but seems no power to boiler. Checked fuse on isolator switch and thats ok. Is it likely to be fuse in bolier or even fuse on main fuse box?