Having researched the various possibilities we're going for the simplest, quickest and cheapest option, for the time being ie: retaining the entire dreadful vented ch & hw set up, with a single coil electric emersion for hw back up in the top of the storage tank ... and "just" replacing the oil fired boiler with an Amptec 9KW or similar ... Appreciate that a 10mm cable needs to be run for the Amptec, but is there any reason why we can't simply cut the 22mm copper boiler-cold-in & boiler-hot-out pipes ... and fit the in-line boiler into the "gap"? (Apart from getting wet of course) Might we be able to retain the present controller as well? I'll be asking the same questions of Amptec but any pointers would be appreciated. Thanks. Mike.