Factual error: The place where Jamie is writing his novel is revealed to be Marseilles, France, when he flies back to propose. In the first part of their story, it might have been Portugal; his housekeeper spoke French, which is a common second language in that country; and Aurelia only spoke Portuguese. Yet in the entire second part, no-one speaks any French at all; only Portuguese and a few words of English. Sure enough there are many Portuguese families living in France; but they do not have their own linguistic enclave in Marseilles, and any generation growing up there would have learnt French as well. Either the language or the airport name are wrong.
Suggested correction: In the second part, only a few people are heard speaking Portuguese, and they are mostly Aurelia's family or friends of the family. It's reasonable to assume that these few people would speak Portuguese, not French.
But they would not speak only Portuguese and live there with a business and everything (even supposing that Aurelia had only joined them recently). And aren't there various neighbours, bystanders, and restaurant guests too? (Hence the closing remark in the original mistake entry about there not being an enclave there.) It still looks to me like the movie doesn't quite know whether they're in the South of France or in Portugal.
Factual error: I know it's a romantic comedy, but no way could an eleven-year-old outrun airport security, find his way around an airport without getting lost or caught and be returned to his dad without even a telling off.
Suggested correction: As you say, it's a comedy; some suspension of disbelief is required throughout.
Factual error: When Billy Mack hears he is No. 1, the DJ, (Radio 1's Wes, who does the chart in reality) says the two singles which could be No. 1, then announces Billy is and plays it, without playing the no. 2 song first. The chart is done as an uninterrupted countdown, so even if it's known what no. 1 will be, they'll still play the "losing" song before it.
Suggested correction: In this instance, the DJ broke with protocol.
