I have the same quest I guess, I really want to know what song that is. It isn't on the soundtrack of Love Actually. But I'm guessing that I think that it might be a song from Howard Shore, the man who made the score (not the soundtrack) for 'the aviator'. Here is his tracklist, I haven't found the time yet to download/buy this record: http://www.cd-reviewers.com/reviews_B0006TYIN0/keyword/aviator
I'm hoping that the searching ends soon and I can enjoy that amazingly good written song.