Hi Wishfullthinker. How old is your boiler by the way? Coz over time, boilers do lose their efficiency and you start to experience problems. If your system is old or you suspect a more serious issue, it may be worth calling a qualified heating engineer to help you out.
Hi guys! Simon here. I'm a professional plumber based in South London and provide my services within the Greater London area. Glad to join this forum and looking forward to help you out with any issues or concerns about plumbing and heating.