I had to wait 2 days. Literally my second day of riding in them and its -5. great.
I mean, 0 would have been ok. I'd have been ok with 0. 0 is cold enough.
It was a cracking morning, my ride didn't get above -4 until I reached the outskirts of Staines where it maxed out at a balmy -2.5
Honestly, the boots were good. It was below freezing and my toes knew that but they were cool with it :) . I could have ridden all day in those temps and my toes wouldn't be uncomfortable.
So yeah, a decent addition, bought just in time.