The social faux pas is one of the fundamentals of English humor. Brits dread saying something embarrassing or offensive in conversation, and so in many of their comedies characters do exactly that. Tim falls victim to this as he encounters that goddess among women, the girl who rejected him, Charlotte, when Mary declines his invitation to the National Theatre and he takes Rory (a.k.a. Roger) instead. He sees her, steels himself, and then steps into his first embarrassment when Charlotte introduces Tina as her "girlfriend". Charlotte is quickly offended at the misunderstanding when Tim casually suggests she is gay. He excuses himself, restages the scene, and this time suggests that she ought to be careful with the use of that word "girlfriend" lest someone think she is gay--which raises Tina's hackles because she is gay. So he redoes the situation again and attempts to avoid the encounter entirely, but Charlotte notices him and descends upon him and Rory with Tina in tow. The meeting goes well--too well, in fact, as moments later Charlotte has discarded Tina, invited Tim to dine with her, and cold-shouldered Rory out of the invitation, then over dinner suggests that she may have been mistaken in rejecting his previous interest in her, and attempts to lure him into her apartment. He declines the invitation, saying that there is something else that he has to do at exactly that moment. He races home, awakens Mary, and tries to ask her to marry him, but she is not pleased at being awakened and shuts him down before he has had a chance to say more than a few words.
True to form, he decides to back up and try again, this time to do it right. He hires a band to play in the outer room, brings a ring for her finger, and kneels beside the bed and awakens her. She puts the pieces together and realizes that he is proposing--no mention is made of Charlotte's impact in this decision. She accepts, and thanks him for not making it too big of a production; he steps into the other room to "turn off the music", and quietly dismisses the band.
The difficult part in this really is, when did he get the band and the ring? He might have gone back a couple hours, vanishing from the theatre and erasing his meeting with Charlotte, and rounded up a band, but it's late, and twenty-four hour jewelry stores are rather unusual. He might have gone back to that afternoon and erased most of his day, or even just part of his day, to get the ring--but then, where did he keep it, and why did his doppelganger not propose sooner? For that matter, having decided that he did not want to encounter Charlotte and he did want to marry Mary, why did he not simply go back to that afternoon, get what he needed, and propose then? He has already demonstrated that he has no objection to reliving a few hours, and whatever kindness it was that gave him theatre tickets he could easily forego the show on the grounds that he had decided to propose to his now fiancé. (He has already joked that visits to the National Theatre are a good opportunity to sleep.) Particularly since he already knows that awakening her when he gets home late from dinner after the show is a bad idea, and he has to travel back some time to get the ring (not to mention the musicians) anyway, why did he then return to this moment to pop the question?
He apparently did not think through it clearly. Of course, that is one of his recurring faults, that he does not think through what he is going to do before he does it. Somehow, an impulsive person with time travel abilities seems a bit dangerous. Of course, Tim is at heart a very kind person, so if he is aware of having done damage he attempts to repair it.
If you have lost count, we have covered ten trips to the past. There are as many still ahead, but not quite so many issues, so we are more than halfway through.