I used to work in Soho years ago and have seen a staggering amount of celebrities but never approached any because a mix of fear of intruding and making a twat of myself.
I also live by the "Never meet your idols" motto because I can't imagine really liking someone just to be disappointed because they were off/having a bad day/were generally awful people. But I'll list the ones I've seen.
Several Big Brother contestants like Ayslene, Richard (yes, it was that year).
Andy Serkis had a face like a slapped arse and didn't seem to want to talk to anyone.
Paul McCartney getting off a car and entering his offices on Soho Square. Even if I wanted to approach him he had 2 bodyguards with him.
Kristin Scott Thomas is tiny. I've seen her passing by talking to a man in French and she was utterly elegant, absolute girl crush on her.
I've seen Noel Fielding in Camden (where else); a woman stopped him and he didn't seem to mind, was smiling and charming.
Morgana Robinson used to work at a sushi place I used to eat before she got on telly.
The only one I wanted to approach but couldn't because I froze on the spot and started babbling unable to say anything coherent: Aidan Turner at the peak of Poldark. I've fancied the pants off him since the Being Human days and as I was walking by he was coming in the opposite direction in Wardour St. I just stopped and watched him go by and started muttering "Erm...baaa...ohohoh", for the sheer annoyance of my DH 😅
There's a lot of other ones, I'll post as I remember them.