The Colin Firth character, Jamie, meets Aurelia the Portuguese housekeeper when he is writing his novel by himself at a lake house in France. You know they're in France because the French-speaking caretaker mentions that Aurelia speaks neither English, Jamie's language, nor French - assumed to be the native language of where they are. So, France. I believe the road signs we see during the scenes when Jamie is driving Aurelia home are in French, so they corroborate this.
At the end of the movie, Jamie decides he's going to run off and propose to Aurelia, so he flies to the airport in Marseille on Christmas Eve. There are signs clearly marking the airport as the Marseille airport when he lands and gets in a taxi. But when Jamie arrives at Aurelia's house, he finds her entire Portuguese family living there. As her father leads her to the restaurant where Aurelia works, everyone they meet along the way is (or at least speaks) Portuguese. The proprietor of the restaurant is (or speaks) Portuguese, as is (or does) everyone in the restaurant. It sure seems like he's ended up in her native Portugal, but all other signs have so far pointed to France. So, where are they?