Awful workmanship, It’s that sort of thing which, with some certainty, will cause an unfortunate future electrician to need to tear the ceiling down to find faults. Every one of those joints and junctions is wrong in more ways than one.
And I’d take them up not only on the electrics, but in the manner that those insulation blocks aren’t vapour sealed or even foamed in. Particularly so since this will be a bathroom. Humid room side air behind the plasterboard will find its way to the cold side of the blocks via those open slots, and can condense out there. This also means that if the cold side is ventilated (or with modern construction as it should be, a vapour permeable sealed membrane above above), cold air can circulate to the warm side, removing the benefits of much of that insulation. (Small builders , much like your “electrician”, sadly aren’t members of “competent persons” schemes). You could partially fix this with foil backed plasterboard, but since there will be holes in it for downlights, that rather defeats the object.
Gaps should be foam filled, and the whole lot taped over to restore the vapour barrier. Of course this leads to a problem with the electrics, since there seems to be no service void in the system, and nowhere to put cables. - That comes back down to the lack of intelligence in the design made by the builder in the first place.
