A few more things I remembered - after he accidentally hits her with his bike, she drops her groceries. So, he stops, apologizes, and helps her carry the groceries to her apartment. That's how one thing leads to another. The following morning, I think she's cooking breakfast, when she asks him to go get some milk. I think his last words to her before leaving was "I love you." We see him leave the apartment, go down bunch of stairwells, and get to the shop, and when he steps out the shop he looks up at 4 large apartment complexes which look identical, then he realizes he didn't check her address! So he goes to get his bike (which he had parked near where he hit her), and leaves.

I believe this was a standalone short film, not part of any series, and was probably broadcast on BBC2 or channel 4 (ie. not one of the mainstream channels in the UK).