Tirglas, you know this is shyte work, so you've just got to have the courage to face them down, and tell them that the works shoddy, and do they intend to fix the faults, or to walk away now, and you get someone else in to sort out the problems, and then pay them the balance less the remidial work.
They haven't left enough cable to fit the fan, hence they've had to use the wago connectors. The lack of a tube through the walls for the fan is completely inept. The fans sticking away from the wall because they also haven't inserted the rawlplugs deep enough (possibly because they cracked the tiles by using the hammer function) but it could be argued that you don;t have to use every fixing. A fused spur is used when you change from say 2.5mm cableing to 1.00mm for the outsiide lights, so there may be a valid reason for it, but the installation of it is just shoddy.
Have you checked their qualifications, as you may have cause to report them to one of the governing bodies, or is it being done under a building control notice.