Autolycus wrote:

I'll shortly need to cut a number of wall panels to length. These are a
sandwich of lightly ribbed steel sheet (0.5 - 0.7mm) and a 70mm foam
core. I'll have around 40metres of saw cut in total.

Saw some long B&D Piranha jigsaw blades today, 132mm overall length,
101mm of teeth (in a progressor style, which is to say deeper wider
spaced teeth at bottom, gradually becoming shallower narrow spaced teeth
at top)

Rated for 65mm cutting depth of wood, 30mm of aluminium, or 3-10mm of
steel, so I'd imagine they'd cope with your composite stuff ok.

Part number X26052 in case that helps, I bought some "just in case", I
did have a job recently they would have helped with, but probably now
they'll not find a use for ages, but you never know ...