That's a major production blunder. Did the car window reflected a bus shelter advert board promoting Doctor Who? Since that's a BBC show and they couldn't mention it (hence the lack of reference in the dialogue), they should've either reshot the scene or digitally erased the reflection.
“A major blunder” you sound like the Daily Express.
I expect they noticed it in post production but left it in, as at worst it’s just caused slight amusement, and at best, nobody noticed it.
Of course it wouldn’t be in the script