Respro Foggy Anti-Fog Mask (Kevlar Look) From  £22.99

What a difference, fit one of these in your lid, no more steamed up visor, even on a chilly morning, nothing!! Takes an hour or so to get used to but very comfortable. Only one very minor thing, you have to just hook it with one finger when taking the lid off or it catches on your forehead (but then my lid is very "snug").
Can't recommend enough, just brilliant.