Went to visit these guys a few years back...
They have grown rapidly, and are extremely well set up! I would always recommend giving them a visit and taking a look around!
They have different pale scales for testers, installers and reactive guys -
I'm pretty sure you'll start on the reactive side, and as you said that'll involve various small works - melted dimmers - lights tripping etc
The thing that put me off on this occasion was that your hourly rate is only earned when on a job....so you won't get paid for any travel time, no matter how long or far. You'll be given an area say South London and cover all jobs within... so don't get me wrong you could potentially earn great money!
But you could also travel to only 3 jobs over London in 1 day!?
I imagine once you have established yourself within you'll be able to climb the rates scale and the controllers will issue you with multiple local jobs...after interview they will offer you a day out with an engineer...no doubt this would be 15 jobs on the same street though!
But....I'm fairly sure they offer a day rate now too? So at least you can have some consistency!
Hope this helps!