Andy BB
Bike gear is pretty amazing nowadays, and you don't have to pay the earth to get decent clobber. Check out Ride magazine for their best buy articles. Personally, in winter I would thoroughly recommend a heated waistcoat and gloves (in handlebar muffs in really cold weather!) I still use Widder heated waistcoat and gloves, but they stopped production years ago. Gerbing do some great heated gear I believe, along with a number of others.
My experience, with snowscooters and motorbikes, is that electricly heated clothing is dependant on a constant supply of electricity, and you cannot move away from your vehicle, or turn the motor off.
Should you have a short circuit or break in the wiring/ plug you are going to get very cold very quickly.
Commuting in the UK this is probably not a big problem, long distance and/or harsh conditions will soon introduce you to hypothermia, and you dont want to go there.
The Primus Rally, 22-24 februar, is a good venue to test your gear.
Peter, in Oslo