Hello,
The days of 'Fred' in his garage fitting windscreens the same day and taking about an hour or less to fit are long gone,
99% of new cars have to be calibrated using the latest equipment by properly trained fitter technicians.
Each car will be different to recalibrate to a very high standard , a few degrees out will mean a few feet out or more for all the safety systems.
There are thousands of different size/shape windscreens for all cars, Autoglass couldn't posibly stock each one and usually stocks the most common ,which makes perfectly good financial sense. The Jazz regretfully isn't a high volume seller in the U.K.
Nearly all garages ,including main dealers , sub contract all the windscreen work for purely financial reasons,in fact the actual replacement screen doesn't have to be a genuine factory made item,this is usually stated in the small print of your car insurance. For example a certain high quality car manufacturer sells a 'genuine' screen with their makers name etched on the screen for about £1,000 ,the same screen from the same screen manufacturer as the original but less the name retails at about £400 !!
This is a strange fact that applies to not only car windscreens but hundreds of everyday items , we in the U.K. are badge and name snobs and the manufacturers take advantage of this.
I was told these details from a fully qualified windscreen fitter ( a close relation of mine) and camera etc calibration technician with 25 years experience.
He works for one of the biggest windscreen replacement company in the U.K ,I can't reveal the name for obvious reasons.
Cheers Neale.