Louis Garneau Glacier; £90 from
Evans.
As you can read in the review, they aren't strictly speaking boots, but shoes with an integrated overshoe: halfway between a boot and a shoe.
I've worn them with Summer socks on milder days, through Spring/Autumn socks, Winter socks and Winter socks with women's tights at 5am in the morning with snow on the ground.
On the coldest/wettest/longest rides they aren't impervious but nothing would be. Even the best overshoes I've had were only between a third and half as effective and were compromised much more quickly.
For the price of three/four pairs of overshoes (not too mention the damage to your Summer shoes) they're far more than three/four times better.
I'm not trying to argue that these particular boots are the best out there, but that boots in general will outperform shoes plus overshoes every time and under every circumstance.