In reply to Jim Houghton:
Definitely a question for you to take to your EVC, and which I suspect they will have to refer back to the LEA for confirmation - this isn't the sort of thing you want to take a best guess at.
I am quite certain (as I was an EVC and am still an instructor) that if you're working with only pupils from your own school, and within remit, then the LEA's insurance is perfectly adequate - it covers everything, including PL.
However, as you're abroad, you're out of remit. So as far as your IFMGA is concerned, you're no different to any other teacher with a group of pupils he may have taken on. He may well choose to take more pupils than he normally might, on the basis that you're rather more competent than most, and he might delegate more complex tasks to you than he would with a teacher who's never belayed before, but those are all going to be decisions he takes within his own professional capacity and thus will be covered by his own policy.
So my first guess is, you won't need extra cover. But if I were your EVC there is no way I would state that as fact without a phone call back to the LEA to make sure!
ps:- are you sure that it's PL cover you're actually worrying about here? PL would be against, for instance, you dropping a rock onto a passer-by. I suspect what you're actually asking about is activity cover, in case you injure one of your pupils? None of that changes what I've written above, though.
