Ok, job done :D
A public word of thanks to Alan Brason of Cullercoats/Whitley Bay, he repaired the issue with my Les Paul's nut today free of charge.
It was a ten minute job of filling-in the low E's slot, then recutting it. However, it was still his time and expertise he was giving regardless of how small a job it was.
Great guy, going back to get the frets re-profiled in a couple of weeks when we have a small break from gigging (August is looking to be a quiet month).