Continuity mistake: When Bridget is dancing at the beginning with wine glass in hand, on the way to the bed she's seen carrying a wine bottle, then it's back to the wine glass.
Other mistake: When Jack confesses to Bridget that he lied to Mark, there is a landline telephone on the table beside her. When Bridget goes into labour and Mark throws away his mobile, they wonder how they will phone for a taxi, ignoring the landline.
Plot hole: When Bridget phones Mr. Darcy, she is told that he has left and is in a taxi on his way home, so Bridget decides to walk to his house where she sees him get out of the taxi and meet his ex-wife at the door, and Bridget thinks they are back together. The problem with this is that she is heavily pregnant and she walks a fair bit across London - hard enough to do at the best of times - and that Mr. Darcy was already in the taxi going home, but she managed to arrive at the same time at his house.