There are some building works that you shouldn't perhaps undertake yourself. Plumbing is one of those jobs, certainly anything to do with the Gas mains you shouldn't touch as that is an offence, fiddling with an Oil burner can have disasterous consequences as, as with Gas boilers the Carbon Monoxide level can be altered by the untrained. If you're looking for the efficiency of an Unvented Heating System this needs to be done with a high level of knowledge, and you  should also take into consideration the insurance liability and danger to the fabric of your home by doing General Plumbing incorrectly. By employing a professional plumber you can rest assured that your heating and plumbing needs are carried out to regulations and that the work is insured.