First floor joists have been put up and so I'm able to access it safely now. Had a quick check of the weight / tension and it's incredibly light!
Not sure if it's a diffreent cable to the one everyone thought but it seems to have 2 principle wires to it (possibly copper coated steel wires?) and it's only about 20m to the post. I haven't disconnected or stripped any of it yet though. The existing bracket looks overkill and although most of the neighbours have a similar one there seem to be eyelet ones else where which would be much simpler to face mount on the new brickwork.
Cheers for everyone's concerns, hopefully I'll be able to re-route and reconnect it without the help of Mr BT's henchmen.
