I've given up trying to keep my feet dry, and just use bare feet and SPD sandals nowadays, in the interests of minimum drying time.
Not being nesh, I just take the view that if it's above zero I won't get frostbite so it's just a matter of a bit of discomfort when it's cold, and if it's below zero it won't be wet so I can get the regular shoes out.
Before I gave up trying to keep my feet dry, I found the best thing was winter boots (goretex lining, fairly high ankle), with a rubber seal over the top of the boot to deflect any water running down my leg to the outside of the boot. The seals have to go against the skin, with any longs you may be wearing over the top, precluding the use of longs with foot stirrups.
I used the wrists cut off a pair of marigold gloves, but proper latex drysuit ankle seals from a diving shop would probably be better.
The current front mudflap is half of a cheap hot water bottle, trimmed enough to keep it off the road. It works very well provided I don't go through the deeper water too fast.