Andrew Thelwell wrote:

My questions, then...

1) Would this explain both the apparent live neutral reading in our
main meter box and the tripping of the RCDs?

No, and no. Did your first engineer say what he was comparing the
neutral with to delcare it "live"?

(if it appeared live compared to the live conductor, then that would
suggest the polarity of your supply is incorrect (unlikely!), however if
he compared it to earth, it may tell you nothing of significance).

I always thought RCDs were
only concerned with earthing faults, not live/neutral reverse polarity
type problems

This is true. They detect inbalance between the current flowing in the
neutral and live conductors.

2) I've been using the sockets in that room with no real probles apart
from the trips. All equipment (TV, XBox, amplifier, phone charger) have
worked OK thus far. Is the socket likely to be causing any harm?
3) Is this potentially dangerous?

In the normal course of operation it will not be explicitly dangerous -
many countries electrical systems do not maintain correct polarisation,
and yet they remain resonably safe. The real danger comes in the event
of a fault that causes the fuse to blow. Even with the fuse blown the
device could still remain "live"

4) Is getting this fixed a big (and ergo, expensive) job?

In itself (the reversed polarity) no, it is trivial. The RCD tripping
however could be due to any number of possible causes, and it will be
harder to identify the culprit.

Your help would be much appreciated as I've had surprising difficult
finding any info about this on the web.

There have been many threads on tracjing down the cause of spurious
trips on RCDs in this group in the past. It may be worth googling for a
few...

--
Cheers,

John.

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