try get some commercial work at least....where theres a 3 phase intake & associated equipment....panels etc...
I agree. Quit the company who are funding your apprenticeship and look around for a job as a mate on a commercial site. There are hundreds of jobs about.
In the real world, a few years ago when I had my AM2 coming up, I was worried sick about Pyro as I was working industrial and hadn't seen much beyond SWA, arctic and wiring cabins. Luckily, my boss was a nice guy and when I asked him he got me some pyro tools and a few lengths of pyro to strip while work was quiet.
In short, just mention it to your boss. Hopefully he'll be able to explain that the 3phase work in the AM2 isn't too different to the single phase work you're doing. He might even be able to gather some materials about to practice a bit. No harm in asking.