On the Grub boots... I've just retired my FROSTLINE boots for the winter, having sat out Friday when air temp was 3 degrees most of the day and my toes were chilly, even with my thick socks on. Saturday evening I wore my SNOWLINE boots for the first time, air temp was about 6 degrees and I didn't have thermal socks on. My feet weren't cold but neither were they toasty. I imagine if I'd worn them with my thermal socks they would have been toast.
I think what we need to remember with most of the these 'stylish' neoprene boots is that they are designed for keeping feet warm when active, and I've no doubt even my Grubs Frostline would keep my feet warm if I was moving about and even if temps were freezing. But not so when sat static. The warmest static boots will always, IMO, be the skeetex type with woolly liners etc. Problem for me is that I just cannot walk far in this type of boot.
I have ordered a pair of thermal liners to go in the Snowlines, felt base with a woolen top layer. I did already try some cheap ones off ebay, but they were wafer thin and have worn down to nothing in about 3 or 4 wears (gets what you pays for).
Anyway, it hasn't been that cold yet...