If you run your fingernail across the scratches at right angles, if the scratch is deep enough to stop your finger moving, you're probably doomed.
Try car polish - gets rid of very shallow scratches just fine. Worth a try even if the test above fails.
If you end up having to replace them, use a glazing company. Anyone involved in selling double glazing will be double the price of a glazier.
Good luck.
Vin