Don't think its any replacement windscreen Chris, just badly fitted ones. Only way to know for sure is dealer or ask around to see who others have used.
Had a look on a few other forums and they seem to prefer Autoglass, Also found this,
I had mine replaced by Autoglass and they used a genuice Audi screen. No complaints, I did have to wait a few days for them to order on in though. Personally I would go to one of their depots instead of getting someone out to your place of work.
Only because unless it is a perfect day, few and far between in the uk, any moisture in the air can effect the sealent.