Sorry to come into this topic so late, have been on holiday (where it was nice and warm!)
I too suffer from extremely cold feet and have tried many and various methods of keeping my tootsies snug.
I have tried short cycle socks with calf-length ski socks over, trainers (which I always cycle in), then overshoes. It does keep the wind off your feet but within 30 mins or so my toes have gone numb and an hour is the absolute max I can be out riding in the winter, however hard the ride.
A qualified health and fitness instructor (who runs seriously in all weathers) recommended trying flight socks. The idea is that they ensure proper blood circulation thus supposedly preventing cold feet. Have bought a pair of these socks (DON'T spend 15 quid, you can get them much cheaper than that - try Amazon or your local BodyCare shop). but have not put them to the test yet.
I also spent 15 quid on a pair of heated insoles from
Maplin - like a normal insole, you cut them to size (gent's 8 is the absolute smallest they will trim to without cutting the heating element). Unfortunately I didn't realise they would only trim to 8, and as my biggest shoe is a 6 I can't fit them in. The heated part is under your toes/ball of the foot area and only produces marginal heat, probably not even felt under even one pair of socks. Also the battery pack is a little bulky, attaching to the lower leg with a velcro strap.
Might try Sealskinz though - absolutely need something to keep Jack Frost from reducing me to a heap after a shortish ride, when I can't feel my feet and fall over!
Otherwise, it's a turbo trainer next winter!!