I have a combi boiler that is on its last legs so I want to get it replaced.The flue currently goes through wall which is at the back of neighbours garden this has never caused any problems but someone told me this is not allowed.The problem I have is it's the only place for the boiler to go apart from running a flue right through the flat which would be a nightmare.I need to know whether it's allowed as it's never bovvered them in the past or whether you could extend up higher with a plume kit.