When I went to Argentina I used multiple comparison engines. The offers change all the time.
The main key thing I had to do was look into the detail. The cheapest policies usually have some pretty extensive up front payment requirements and some very restrictive conditions on what you do if you actually need the insurance.
I found that differences of a few pounds on the headline rate could become hundreds if you actually needed it.
There are 10 types of people in the world: Those who understand Binary and those who do not.
Eurotunnel insurance - you don't need to book any travel with them. Absolutely brilliant, they even insure me Go online to Eurotunnel then I think you phone them.
We use Insure& Go. This will be the third year we have been with them. Office is in the UK. Very helpful staff. One of the cheapest but good cover. You can see the policy before you book so yo know what is covered.