Hi Leystan, I checked my MOT and it's due on the 25th June so it sounds like you may get there before me.
I'm in the position that if I uncork it then the reservoir will empty itself in about 2 minutes, meaning the windscreen washers won't work either, which would definitely be an MOT fail.
A new sprayer nozzle is £61 from BMW and if mine fails the MOT, then I'll just have to go for it and get that.
From what I've read, the leaking issue comes about due to the parts freezing in winter and cracking the plastic so I don't think it's even like I can replace an O-ring or anything like that.