Rear Glass / Condensation

[1781cc]

My rear glass has condensation on the right lower part and I wondered about the best way to get this resealed?

I just spoke to auto glass and they said that the can't guarantee the glass will come out in one piece, so can only be booked in as a replacement, to the tune of nearly £600

What has everyone else undertaken to solve this condensation issue on the D3 S8? I am guessing its a seal that has perished or separated as I have no sunroof, so its obviously not sunroof drains

Any help appreciated!