They are apparently available rewirable with a strain relief, but I'm not sure where you can actually buy them. I used to work repairing appliances and items with strain relief boots the flex often used to break internally or the sheath split at the end of the boot rather than at the plug so...
Perhaps there is a faulty temperature sensor or a triac controlling the elements has failed short circuit. I've installed loads of these but not had any fail yet to need to do any fault finding.
I think this fitting is fully enclosed, but some open type GU10 fittings you can replace the lamp from the loft space above if it is accessible, to save damaging the decorations.
That's the only one I've ever seen in the 23 years I've worked as an electrician. (I've seen the little 2 way 'extenso' extension boards that of course don't have a main switch but never a full sized one) It's not modified, there was no hole in the cover for a switch.
I'd be more concerned with having the electrical installation inspected and tested rather than fitting different light fittings. Not sure I've ever seen cable with only red and white cores, except for speaker cables.
Why not, decent inline fans offer superior airflow through the same size duct, reduced sound levels and a longer duct run will cause additional restriction from backdraft compared to a 1' pipe through the wall. One of the first jobs I did when I moved into my current house.
Too late now, but we always try to avoid wall fans where possible. High quality in-line fans are more powerful and a lot quieter/ no back draughts etc.
Probably not great to drink from it. You can buy kettles that heat water with mains into 2 stainless steel strips. I did it with mains and 2 tea spoons a few years ago, I probably drank it at the time but don't remember any specific taste. I wonder if that's why I'm going bald...