This failure is not uncommon on this generation of 1 Series, although that does not necessarily mean a dealer will be willing to give you a discount on a replacement. However it is worth trying, particularly if you can provide a receipt or invoice for the replacement on the other window, so ask the dealer to raise a goodwill request with BMW UK. If this is unsuccessful a better option may be to take the car to a reputable independent BMW specialist who may be able to recommend a more reliable replacement part and will likely cost less than main dealer prices.