SJA Checklist-- "Secrets of the Stars" part II.

Crowds of people walking through London under alien influence: Check, check, check.
Tie-in with Doctor Who story: Non-check, though Alan said, "they might as well just have said 'Mandragora Helix' and have done with it."
Girl protagonist's mum is annoying: Almost a non-check, but her folksy twinkle over Dad's cooking at the end just did it for me.
Mobile phone as plot device: Semi-check, as Clyde's remarks about not having a mobile meaning a loss of identity ties in with Luke's worries about his lack of birthday meaning a loss of identity.
Luke says something so daft that you have to wonder how he gets through life without being mercilessly bullied: Non-check; the idea that there was a universe before this one where astrology worked is total bollocks, but as it's part of the premise of the story it doesn't count.
Sonic lipstick: Non-check.
Wristwatch scanner: Non-check.
One or more of Sarah's companions falling under alien influence: Check, though I was expecting they'd get Sarah too.