Lee,

A PTW on a domestic would be unusual.
I don't see it as a legal requirement, and certainlydon't implement it within my organisation.
Normally with such a simple install and a single point of isolation for the whole installation, normally a SSW would be the norm.
The electrician working should be responsible for his own isolation and "prooving" dead of the circuit.
Remember, "Prove Dead, Stay Alive".
Sorry knicked that one, but is is a good saying.
Multiple lock off's on a small domestic board can be difficult to implement, though not impossible.
Also pulling the DNO fuse is NOT an option.

HTH
Paul.