17th ed shallow buried non-RCD circuit in metal conduit OK?

[GaryMo]

(If you do happen to use flexible metal conduit, then if you need an earth connection at the far end you will tend to need to feed through a separate suitable CPC wire.)

I would install separate cpc's whether it be flexible or solid metal conduit.
In any case, I've only ever used flexible metal conduit on machines and industrial applications.