Manufacturers of twin and earth cable, it's been over 50 years and a change of colours since the wiring regulations demanded sleeving on the earth wires, so why isn't it built into the cables. The extra faffing that the loose bits of sleeving adds would be removed, making the marginal extra cost worthwhile.
Professional electrician who has done some wiring on my house, it was only 3 lights and a fan in the bathroom, with a single pull-cord switch. The fan needs permanent power as well as switched. There's a shaver socket as well, and cable from the fuseboard and a cable leading to the bedroom lights. Nothing too difficult, but you managed to connect switched power to both connections on the fan, use three 4-way junction boxes when two would have been fine, not use the cable clamps in the junction boxes correctly, loose a screw from the lid of a junction box, fit a single terminal block to extend a wire inside a junction box instead of stripping a bit more sheathing (in two places) and join two earth wires by twisting only, hiding the evidence inside the earth sleeving.
I realise that I am under qualified* to comment on someone who does wiring for a living and has the part P training.
*Electronic engineering degree
