Actually, thought that I should mention the bit about testing for interference. Every electrician chooses their own equipment so some will have better capability than others so its worth asking if they will be testing for interference and to what extent.

I had two sets of independent tests, one set commissioned by my potential purchaser (who eventually used the results to pull out of the purchase) and another set commissioned by myself (who used the results to fix a couple of defects) and bring the installation up to 18 edition wiring spec standard where safety would be improved. The capabilities of each was excellent however their test equipment worked in different ways.

One piece of test equipment was sensitive enough to pick up my X10 switch gear and a low voltage transformer putting noise on the line whilst this was never commented on by the other so I don't know if they spotted these or not.

Meridian owner since 1992
Prime & PSU, Focal Elear headphones, Roon (ROCK 8Gi5 NUC), Explorer 1 & 2, F80. 200/203, various Sonos (via Roon).