They should've made the movie like Sliding Doors
Here's how it would look: After the airport scene, the movie alternates between two timelines: The timeline where Jack goes to London, and the timeline where he doesn't.
In the latter, Jack begins to regret his decision, so he's also given a glimpse. He sees what his life would've been like if he did go to London. At first he enjoys it, but then starts to miss his old life, which he of course eventually returns to.