I don't think your local DNO will allow you to keep your original single phase supply I used to work for London Electricity in its various names over the years and was always a general rule of one supply per property in new and refurbished buildings
this is a specialised field really mate used to do it when I worked for the dno usess specialist meter echo pulse shows a wave form with reflections where there are faults and joints or you can cut into sections start at the centre and eliminate good sections and re joint back then go again but...
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc