Split-toe O'Neill Ninja Boots:
au.oneill.com/products/heat-ninja-3mm-wetsuit-boot-black-4786-002Boots (not socks - the socks come in S/M/L sizes and don't have a proper rubber sole).
FWIW, I hate cold and don't tolerate it well.. I have average size feet (43), but very long toes. I buy mine same size as shoe size (not one size smaller as people often recommend). Mind you, that's American sizing on their website: 10 US = 9 UK = EUR43.
I've tried many, many different kinds of boots, these are the only ones that you forget you're wearing them. I wore them in 11 degrees water and 13 air and while they weren't "toasty warm", I didn't feel cold either. IMO, at least in Victoria, you don't need super-thick boots, as long as you core and head are warm. So a hood, and something to keep the windchill off your torso. Now I need a solution for my hands.
The downsides of having such soft pliable boots is that they last about a season at most. I bought mine in May and they were worn out by Feb. I wear them all the time (city beach). I do turn them out to dry and hang them in the sun, which may not help.
Atans are the only ones that can compare in this regard. Atans are also warmer, but... they are water proof. So if water gets in, it can't get out. Wearing the wetsuit over the top of the boots helps only so much. They are also more expensive and last even less than the Ninjas. The instruction is not turn them out to dry, but they will stink real bad if you don't.