I have upgraded David, but LATAM are apparently a bit slow in coming up with the prices. I got mine upgraded to Business Class for just under £4K which includes 6 flights, London, Soa Paulo, Santiago, Easter Island and all back again. The remaining flights are economy but they are short haul and there is no business class option.
You need to look at the seat configuration on "Seat Guru" as although they are flat beds the window and middle seats do not have direct aisle access in this configuration unless you can do a slow motion hurdle type move.
However, reviews about the rest of the services are good and price wise very competitive and worth it to me. One other bit of advice is you cant choose your seats online but have to ring customer services, the whole thing was problematic until I finally spoke to a lovely lady that sorted me out. Message me if you want more details