OP
Deleted member 114336
To the OP - firstly all who have replied to you are well qualified people, the only way to meter this persons individual usage would be to have all of the sockets/lighting etc that he personally uses on their own circuits and thus through a dedicated meter.
But I reckon he should learn some respect for others and some decency, a background of neglect is one thing but do you think it's ok to let that cycle continue for ever more ?
People tend to lash out when made to change habit. I have to separate his bill or he’ll leave.