Epoxy resin probably won't do it. As soon as you get up to temperature the epoxy will go soft.
Try Unibond Repair Metal For Good 8000 0078.
A tube of that should cost less than a fiver. Well 2 tubes actually just like epoxy.
Big Softy, June 2006
edit
I can answer this question...
THE PLATE HAS FALLEN OUT OF MY GHD STRAIGHTNERS WHAT DO I USE TO REPAIR IT?