3.5yo sudden bedtime menace

[pharmacoco]

Please help a desperate mum.
Son has been sleeping in own room from 6m. Been in toddler bed for the last 6m. Not had any difficulties settling him. Same routine has been bath, book(s), lights out.
Hasn't napped in the day for about a year. Usually in bed and asleep between 7-7:30pm, is up between 6-7am
For the last week won't settle, gets up, put him back, gets up, wants to sleep on our bed,messes about, laughs at me if I suggest taking his cars away, so I take them away, isn't fussed. There aren't any tears, just laughs.
Tonight I went downstairs and he pulled the gate off the top of the stairs and thought it was hilarious.
HELP or advice WELCOMED

When my 3yo does this I just get in bed with her and ask her what she wants rather than getting annoyed - usually she says “I just want you mummy” I don’t think it’s even FOMO she just wants to fill her quota of mummy cuddles and love (even though I think I fill it all the time!). Other times I say it’s fine to play in your room and then shout me when you want tucking in and always within 20 mins she calls me back to tuck her in, I just think she sometimes needs some more time to wind down.

Does he just want a bit more time with you? Can you do more books, set an amount and tell them at the end of 3 books it's time for bed?
Or ask what he wants to do before bed with you? Jigsaw, game, reading?

Will try and see if he wants 'something else'
Invariably he's had an hour to 90mins of playing whatever games / activities he likes with myself before the bedtime routine starts but who knows !!

@stripydungarees I'm impressed she stays in her own room and plays. My son would be out that room, despite the toys in there!