ive seen some foreign dudes using alarm and cat 5 cable wired to the mains, on the other hand ive seen some top notch work done by polish lads that a builder i know employs.
ive spent the last 3 years renovating my gaff and ive not let anybody work in it apart from a plumber and a plasterer. gradually learning more about plumbing as i go on but even i could have done better work than shown in that vid.