Yeah - actually I have upgrade my order with BrassCraft to a heated screen for the Cobra
Given that mine steams up at the first sign of humidity, sounds like a good choice
Not cheap though - adds ~£200 to the cost of the screen.. and Chris isn't quite sure about them yet as he hasn't done many (or any, possibly!). Still, should find out in ~3 weeks or so whether it worked as that's about when my screen should be ready (and wind wings, visors, fuel filler, etc etc).
Might not find out how well it demists for a while though as there's still no drivetrain in the car!
Still, it'd cost £200+ to fit a proper heater, which is the next best option given that the electric blowers aren't much cop except for getting past the IVA. Less weight, too.
Then again, I've been glad of my proper heater on many occasions, and, even when I can put up with the cold, it stops the rev limiter complaining (about the cold, not the driving).