I got a low tech nibbler that attaches to a cordless drill. I'm almost certain it was this one or at least one visually identical. It did the job perfectly fine but you do need to angle the tool to follow the curvature of the corrugate which can be a bit awkward (in my case I was trying to do it in situ but on the ground would be easier).

Having said that, I have a builder friend who possesses the correct Milwaukee tool for paying clients, but when we were working on his own shed one weekend, he used a cutting disc on a grinder. After chalk-lining it, he cut 5 sheets in under a minute. I guess time really is money when no-one is paying you...

He said if he was pedantic about it, he could have masked off the edge and blown some rattle can paint in the applicable Coloursteel shade over the raw exposed edge, but because the cut edge was going up under the ridge cap and would therefore always be out of the weather, he didn't see the point.