I have just purchased an SL500 (1997) at night the glare on the front windscreen from other cars headlightsis horrendous, is this common?
DoI have to but a new windsceen or is there something I camn put on the screen to stop the glare (the windsrceen fitted at the moment is a Mercedes windscreen)

 

You might try a good solvent cleaning of the windshield before doing anything drastic. Use something like enamel reducer or Bug and Tar remover available from any auto parts store. If you use a white cotton wiper you should be able to look at it and tell if you are getting anything off the glass. Follow this up with a good wash down with hot water and Dawn dishwashing soap. Use only a soft cotton wiper for both cleanings. If there is any heavy road film or tree sap or some other contaminate on the window this will take care of it. I onceheard of a fellow that used steel wool and terpentine on his windshild to remove paint overspray. The steel wool caused very fine scratches in the glass which caused a condition like you describe... he had to replace the windshield...I hope you can avoid this.
Ken

 

I had very fine wiper marks in the windshield of my 96. I purchased glass polish from Griotsgarage.com and their random orbital buffer (also got the clay and paint polish and wax). Used the glass polish on the windshield with some improvement. Reapplied Rainex. Did get caught in a storm before reapplying the Rainex and thought I was driving "blind". I'm spoiled to Rainex though. I had already tried various cleaning products with no improvement. Did "clay" the windshield first!