Several issues spring to mind. I have had a peep at E-Bay and note that many of the diesel heaters are made in China. Firstly they all appear to state that Professional installation is highly recommended. Secondly I do wonder whether they meet the required UK standards? This is important because your boat needs to have a toll paid and the boat itself insured. For that to happen you need a valid boat safety scheme certificate issued by a BSS inspector. This is as much for your safety as it is for the safety of boats moored near to you. The BSS certificate covers not just the heater but also the installation, fuel supply and ventilation. Without that your mandatory insurance will, I suspect, be invalid. Sorry to be all heavy but a heater has, I'm sure, to be installed safely and suitably certificated. Big brother is watching!!