[Tom!]

We use a narrative rather than a cover letter.  This accompanies a standard application form which covers the data included in your resume as well as other info we need.  For our purposes this is to tell us about the person rather than the worker as well as their reasons for wanting to live and work overseas.  Also to explain to us that they are normal and we will get along as we work in small groups and have the potential to be dealing with this individual at off hours as well.
When i was corporate the letter was used to sell myself to the company.  I would always call HR first and plant the seed in their head.  THen when the cover letter arrived there, it made more sense to them as the info was fresh and came along with a frame of reference.  Going cold never worked for me and it was explained to me by HR that due to the amount of resumes they receive, they are forced to skim through the pile before shredding most of them.  Do whatever it takes to help your resume to jump out in the 30 seconds its being reviewed.  The cover letter can do that for you.