Maybe her grandmother lives closer to the London Bridge station, or they were at a restaurant closer to that station.
Here is my interpretation: I disagree because I interpret his newfound presence and comfort with being filmed with a sense of pride about having purchased or rented an apartment. Perhaps he read threads here and was aware of how comments were making him out to be some type of freeloader off of Tiffany, that he was living rent-free in Tiffany's house. Thus, he preferred to remain off camera. Now that he has a place of his own, he is, all of a sudden, so comfortable being filmed. Also, I think the place is Matt's because I notice that, aside from trees, there aren't indoor Christmas lights lining the walls, similar to what is seen in her Croydon house. Probably Matt told her he doesn't want all that clutter in their new place.
Here is a still shot of the doormat, the literal doormat:
View attachment 2630185 q
Unless they keep their shoes outside, which they don't do in the Croydon house seeing as how the entrance hallway of that house is lined with shoes, this doormat is indoors.
The little portion of masonry of the walls around this entrance door looks like indoor, not outdoor, masonry.
This may be the entrance to an apartment.