I have a replacement screen but I haven't summoned the courage to do the job yet, I'll probs wait till summer.
I did find something on the net about it but true to form I can't find it now. I'll see if I printed it out when I get home.
general technique for windscreen in general is:
if you want to make sure the glass gets out intact, cut the rubber out
if you want to make sure the rubber is intact, break the glass.
if you want to get both out intact then its trickier: From inside the car start in a top corner and with a flat blade screwdriver, push a small bit of the rubber over the body lip so its outside the car. Placing a careful amount of pressure on the glass (probs with your feet, or those of your beautiful assistant) continue popping the rubber over the lip all the way along the top of the glass. Then do the sides and then remove the glass. Doing it this way risks breaking the glass.
to get it back in (after you've sorted the rust) put string inside the rubber lip crossing over at the bottom. Cover everything in fairy liquid and then place screen in place at the bottom (with the ends of the string inside the car)
your beautiful assistant applies pressure next to the string as you pull the string. The string is not supposed to slip around the glass and all being well the string will pull the inside of the rubber seal over the metal body lip. Your assistant will be following your progress and placing pressure directly next to where the string is pulling the screen into place.
Sounds easy but is generally quite problematic, I've done this job on fords and VWs but never a bimmer so all the above might be slightly wrong!! I've only broken two windscreens to date
Edited by Drew21