I have a few!
Matt Damon - only a brief interaction but very pleasant indeed. He was much bigger than I'd have thought, not tall but extremely wide :)
Lulu - met her in a loo in a restaurant and she was really chatty and nice to me and very little DD, it was not long after lockdown had ended so maybe she was extra happy! She went out of her way to speak to us rather than the other way around, I didn't tell her I knew who she was (same with Matt Damon) but she didn't seem to be doing that whole 'do you recognise me' thing. Whereas Geri Hallliwell (who I only walked past once in South of France) was DEFINITELY doing the whole do you recognise me thing, with three massive bouncers to keep people away (and attract attention, she was so small that if she'd just put on a hat and kept her head down, you'd never have known it was her!)
DH was shopping in London supermarket when he realised he was looking at the same shelf as Kylie! Tiny and very very unassuming, he said.
Neil Morrissey - not a fan of his actually but he was really very nice, again only a v brief interaction.
Eddie Redmayne - he apologised to me when I bumped into him (by accident) in a dept store - he was on his phone so it was an extremely brief interaction but he was very polite (and insanely beautiful).
Penelope Keith (!!!) was really lovely and charming to my gran when she approached her in a car park and told her what a fan she was!
Sat next to most of Blur in a restaurant once years ago just as they were getting REALLY famous, they were a bit too-cool-for-school but fairly unassuming. They had an aura about them though.
Sat a few tables along from Julianna Margulies in a restaurant once, didn't have any interaction with her so it doesn't really count but she was pleasant to the staff (though have read stories about her being less than nice) and quite staggeringly beautiful to look at, she glowed.
Gregg Wallace (I know!!!) was nice!! Bit of an idiot but quite sweet, if that makes sense.
A friend met Pink and said she was tiny and very nice.
My mum once got in a taxi and the driver was Amy Winehouse's dad (this was some time before she sadly passed away) - my mum had no idea who Amy Winehouse was but phoned me to tell me she'd been in a taxi with a nice driver who had talked and talked all about his famous pop star daughter! :( I think about him every time I read anything about Amy Winehouse.
Have heard from a friend who works in PR that Dawn French was not nice, which made me a bit sad. Same friend says Ewan McGregor charming but a bit sleazy.
An acquaintance is very good friends with Tamara Rojo (ballerina) who sounds absolutely delightful.
Think that's all I can remember!