I got bored of waiting for the screws, sitting there with the board and a 12900K and just waiting for some £2.99 screws.
So after reading some reports on Reddit and the Corsair forums, I decided to just go for it - It is only a 0.08mm difference between the two and mine screwed on well.
The temps, I got were pretty low and cooler than my 9900K - I am just not going to overclock without the proper screws.
But for getting it up and running and not sitting on £900 worth of tech, I would recommend trying it - Run RealTemp for a couple of hours and see what the maximum temp you get.