Potterton Performa safety inspection and service. Around 20 years old and not been inspected for a while.
Needs a little tlc with a common exhaust flue clamp corroding that causes an fumes leak internally within the boiler. This results in the dirty emissions being drawn in again for consumption resulting in significant levels of carbon monoxide being produced. This is prime example of why boilers need to be regularly checked and serviced yearly as whilst its producing heating/hot water, it can sometimes not be in a safe way!