Topr8, yes Amazon sounds like probably the best bet.
Lucy 24 - how can I tell if my audience has lives?! I know that they profile (from a variety of sources) as 80% female, mostly aged 30 - 60, lower than normal education (how do the profiling sites get that info!) and are interested in the home / leisure type of things but not neccessarily travel.
I was trying to think of a globally redeemable prize but it's unlikely I'll get one. So maybe I need to cater only for the 85% who live in the UK, USA, Canada, Australia and most of Europe. I can name the prize in the competition and only those who can utilise it will enter.
Hopefully that wont offend the few who live in a tent in the Amazon jungle (if there is any jungle left nowadays).