I went through the exact same thing last year—it felt like my money was literally vanishing into thin air while I was still shivering. It turns out the issue was a mix of air locks and just a complete lack of basic servicing. You should definitely check out this article https://northpennnow.com/news/2025/mar/04/how-to-ensure-the-efficiency-and-durability-of-your-heating-system/ It’s a great breakdown on how to ensure the long-term efficiency and durability of your entire heating system. After reading it, I realized that simple things like professional cleaning and annual component checks can cut energy costs by nearly 25%. That humming noise you mentioned is often a sign of limescale buildup or incorrect pressure, and the guide explains how to spot those small issues before they turn into a total system failure. It’s much better to do a bit of maintenance now than to wait until the boiler completely dies in the middle of a cold snap!