Hi,
Other than paying using Avios, this has nothing really to do with BA. I think the chances of anyone in the BA forum section of FT having experience are sadly quite low.
I wonder if you would get a better chance of a responce if this question was moved to perhaps the South American section:
http://www.flyertalk.com/forum/south-america-483/
[Sadly they don't yet have a subforum for Chile.]