A hotplate will work fine. It is a passive device, and doesn't need mains power. Also, most pedals will work on your adaptor, you just need to check the polarity is ok.
Carlaz, yes I mean checking at the gate, or failing that, British Airways does hand load guitars and ohter musical instruments. I brought 2 guitars back with me on the plane (and 115 kg of assorted luggage!), and then had another 7 shipped with my other household stuff. The shipping takes about 1 month.