I've done some GL's and GLX's with heated screens before now....

Phone up this lot - Master Auto Glass - 0208 531 9219, and ask for Ben, Marie, or Mick - tell em Matt from Autoglass "across the road" gave you their details and they might be able to do something on the price for you.

They will be able to supply you with a full brand new screen - so less to worry about having a second hand one breaking taking it out and putting it in yours (it happens, even to the best of us ) and also you will have a years gaurantee on the heater elements aswell...

Then find yourself a local fitter who wants a nice cash job to fit it for you. For reference, I would probably only charge £40 or so to fit it (depending how poo the job was - some are worse than others )