Update 4th June....no progress! SSE have come back from their wayleaves dept and said "....The cable that has been exposed is at an unsafe depth and therefore the cable needs to be buried to make it safe. Our solution to put the situation right is to raise the levels on top and around the cable as it runs behind the now removed sleepers and underneath the concrete. In order to make it safe, it is likely there will be some adjustment in the way you use the path in its current format."
I have rejected this bodge suggestion, not least because it will make access into our garden much harder...and its a bodge. I have referred it to HSE for advice. I am also engaging our house insurance legal cover.
Meanwhile the dodgy wall issue is still there....