This really only applies to new builds and comes from Part M of the
building regs (accessibility for the disabled etc) and is not directly
related to the wiring regs. For an existing property the usual rule of
thumb is to make it no worse than it was originally.
Common sense suggests that placing it somewhere where it can be reached
easily in the dark without the need to stand on anything to reach it
is a good idea. 2.3m may be getting a bit high for this to be true.
 Always worth fitting a non maintained emergency light near the CU
powered from the local lighting circuit anyway.
Part M applies to when the house was built - not the place re-wired. If
the house pre-dates part M there are sure to be any number of ways in
which it does not comply (things like a step over the front door
threshold rather than the completely flat path through that lets the
rain in as favoured these days).
Hence the odd non compliance during re-wiring is not going to alter the
overall compliance of the house IYSWIM.
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