I feel you pain! I assume this is a new home for you, or you'd have more information. It may not be a timer issue, I'd check other things first. I can see from your picture that your boiler pressure is fine, so that's good. Have you bled your radiators? If not, that's where I'd start because air in the system can cause all sorts of problems. You do this by going to the highest radiator in your home and using a bleeding valve key to bleed it until water comes out. You may need to re-pressurize during the process if you have lots of air.
Next look for a thermostat and make sure it is set for the right temperature. And that it works properly. After that look into the timer. I don't recognize that one, but it'd bet that one of those buttons is an override to turn it on consistently.
Keep in mind that there are other things that could be wrong, you could have a bad gas supply, contaminated water in your boiler, a bad heat exchanger, etc. For all those you'd need some professional help.