Slow/Spluttery Start when cold or been left for multiple days

Hi, I've got a 2018 1.6 Insignia, and I need help diagnosing a faulty injector!https://youtube.com/shorts/5ccaoHSzH...UHvQKI2fAHSw-p. Here's a video of the car starting on a cold morning after being left for around 24 hours. It does this only in the cold and after being started after 12+ hours. If it's been driven that day, it'll start with no problem, IE if i drive it to work and leave it for 7+ hours, then starting up even if its still cold out it'll start fine. No power issues, smoke, engine lights/warning code. Car drives perfectly fine other than this issue, it will also occasionally misfire on these cold mornings once in a while. Can anyone help with what this could be? I'm thinking maybe an injector (or god forbid multiple), it's booked in at the dealership in a few weeks but i'd like to get an idea first on what it could be/cost if possible.
If anyone could help that would be great! Thanks.

PS, car had an oil change a few weeks ago, this issue seemed worse before this change, and seemed to get a tiny bit better for a few weeks after the change, but this could've also been due to me doing a few long journeys with some premium diesel right afterwards.