In terms of film conventions, it begins with the production companies images
Then there is footage of people hugging in Heathrow, showing the film is about love and care. This clip isn't really 'part of the movie', nor is the voice over.
The beginning also includes credits with the institution and production companies. There is then also the voice over which shows it is about love and care, which is when they also introduce the title of the film. The quote is:
"Whenever I get gloomy with the state of the world, I think about the arrivals gate at Heathrow Airport. General opinion's starting to make out that we live in a world of hatred and greed, but I don't see that. It seems to me that love is everywhere. Often, it's not particularly dignified or newsworthy, but it's always there - fathers and sons, mothers and daughters, husbands and wives, boyfriends, girlfriends, old friends. When the planes hit the Twin Towers, as far as I know, none of the phone calls from the people on board were messages of hate or revenge - they were all messages of love. If you look for it, I've got a sneaking suspicion... love actually is all around."
We also have different shots introducing us to the characters that we will be following throughout the story. We have an idea on background of the characters. For example we see that Liam Neeson's character has recently been widowed and we have expectations that his plot line will be him either finding a new love or coming to terms with his wife's death.
The audience also expects love to be heavily involved because in the opening sequence we also have the introduction of a wedding. Incidentally, it has almost a 'red herring' subsitute in terms of comedy as it introduces the wedding with the best man and the groom standing together. When I first watched it, I thought it was a gay couple until they started talking. Whether this was incidental or not, I don't know.
The credits also include: Casting, Music/Music Supervisor, Co-producers, Hair & Make-up, Costume, Line Producer, Production designer, Director of Photography, Editor, Producers and the Writer/Director.
In this case, the writer/director was very important. Richard Curtis directed and wrote the screenplay for this film. He is heavily connotated with comedies such as Blackadder and Vicar of Dibley. He, too, is British. This film targets British audiences heavily, showing the best of british talent.
Casting may be important here because the cast is majorly the 'Prides of Britain'. Music is important because it determines the mood of the film and most films, including Romance, determine on music to create the mood (in the case the mood of love/happiness)