What the meter should read, and what to do with an unsatisfactory result0.54 megohms on new work. Pass?

What the meter should read

Find the table in Guidance Note 3 · p.70. The table gives the minimum. The number to actually work to is higher:

In practice a healthy new circuit reads at the top of the meter's range — >200 MΩ or >2000 MΩ depending on the instrument.

Unsatisfactory results, and what you do with them

Two worked judgement calls.

Meter shows "greater than" — off the top of the scale.

Check first:  are the leads the right way round? Is the meter set correctly?
              Is the switch operated, if it is a lighting circuit?
Then:         that is an open circuit — a break in the conductor.
Action:       installer pulls out and replaces that cable. Retest from the start.

Continuity wants as low a resistance as possible, so an over-range reading means there is no connection. The consolation: on a continuity failure you have not got far into the sequence, so retesting from the beginning costs you very little.

Minimum in the table    = 1 MΩ      -> 0.54 does not even conform
Expected on new work    = >20 MΩ    -> nowhere near

Verdict:  not acceptable. Degraded or contaminated insulation,
          or a load still connected.
Action:   find the cause, put it right, retest.