I have a discovery 4, model year 2010.

I purchases it without windscreen washer heaters but what I noticed is under the hood/bonnet, I can see the electrical cables running to the windscreen washers for what I assume to be the heaters.

Are the cables fitted standard to all models and then activated and de-actived through the on board engine management or media interface?

 

Most likey you just need to buy the right windshield wiper arms that come with the heated package.