I replaced the drivers door regulator in the wife's 125i around 12 months ago and a week ago had the drivers window 'drop' in my 135i. Rather than buying a complete regulator I managed to track down a repair kit from automotoparts.eu see
https://www.automotoparts.eu/en/sear...r=search&s=e82
The kit cost me 36 euro which worked out at least a quarter the best price I could get for a new regulator and was delivered in around a week. I figured why fork out for a new regulator when the problem was caused by the failure of one cable? (sort of regretted that while I was trying to do the repair though).
Without the aid of any DIY's on cable replacement it took a bit of time to figure it out. Finally worked out a few tricks to tension up the two 'springed' cables that attach the motor drive pulley and now have the old regulator back together with new kit cables, springs and drive pulley. Will be putting the regulator and window back in the morning but will write up a DIY on the cable replacement if anyone is interested.
Armed with the knowledge I now have, it should not take much more than 30 minutes to install the kit so it is a worthwhile alternative to a new regulator considering the cost.