check if your transformer is being controlled via the dimmer switch. Not all transformers will allow the use of dimmer switches to control the voltage/current passing through them.
Great I like it. Yes the engineer might look else where, but who is the designer / installer of the circuit - you, and again you must comply with the regulations.
Ok lets have another go !!!!! where is the pump for the shower? Would it be reasonable to say that at some point this may require maintenance - yes. It is prefered that the person performing the maintenance has the means of switching under their continuous control. If not regulations 462-01-03...
the electrical regulations states that you must have local isolation or means of cutting off the supply to an appliance. Your socket in the loft can not be clased as local isolation, even though a plug and socket is classed as means of isolation. As previously posted what if you need to isolate...
our friends are quite right you do need to look at having your bathroom rewired, with a pull cord double pole switch switching the power on to the transformer for the SELV circuit ( selv usually 12vac rms or 30vdc ripple free in zone 1). then EVERY current drawing appliance and extraneous...