On 13 May, 19:42, andrew wrote:
Could anyone recommend an electric nibbler for cutting box profile 0.7mm
roofing sheets?

No, I couldn't recommend an electric nibbler for doing this.

Nibblers have their place (awkward internal cuts), but assuming that
roofing sheets means "lots of straight cuts, maybe one stovepipe vent"
then you'd be better off with a disk.

Then if you think you need a nibbler, look at a plasma cutter instead.
Even for plastic coated steels, provided you don't need a perfect
surface right to the edges.