In reply to joeramsay:
Hi
Also worth thinking about, you may not be being paid but I am guessing that the centre is charging for the climbing lessons, if this is so and their clients are paying, its not actually you volunteering to teach people for free, the owners are running a business and just happen to be able to get free staff, so any volunteering insurance wouldn't cover you as the clients are paying clients. see this some times in France etc, where people are trying to get round need a cart pro.
Hope you find a way if you really want to go.
cheers