Hi,
I took out a backpack annual insurance for 250 (or there abouts). It covers people who are travelling abroad for long periods of time and will be a country for more than the 30 days which standard policies cover. Though I am based in Canada, I have been to America and visited a few Caribbean Island on this insurance. Plus I plan to travel around North America soon. I got it to cover certain sport activities I knew i would be doing.
I think i used either money supermarket or googled backpackers insurance (not sure). Money Supermarket is good as it gives you a list of insurance companies which you can compare against.
When I get home I will check the name of the company I used and post