Convert to 12v for vocal booth

I'm reasonable sized vocal booth and now looking at the wiring. I am keen to go low voltage (12V DC) because all I will need is a dim light and fan to pull air in and I'd like the wiring hidden (the fan will built within a separate baffle box outside the booth). Is it a simple case of... Buy a 240v > 12v transformer and get a sparky to hard wire to mains. Wire from transformer (outside booth) to wall mounted switch inside which can control fan and light - with this, I'm just wondering if that means the transformer is always on and if that's an issue Or should I just get power points installed outside the booth, plug in fan/ lights then poke the cables through the walls? Obviously electrics are not my forte...