Thanks for your responses.
I've had a proper look at the nozzles, and used a pin to ensure they're clean. They seem clean. The left nozzle seems to be missing a hose, however when testing the washers, nothing comes out of the hose barb. Looking at my F11 that's waiting to be sold, the left nozzle has the same barb without a hose. I know it works, so it must be as intended. The F01's rightmost nozzle, the one closest to the bottle, has a weak jet out of it, but the other two just had weak dribbles not amounting to anything.
The left and right nozzles seems to have detached from the bonnet at the rear side (facing the windscreen) but isn't affecting the performance at all. The middle nozzle is nearly detached but that's not my issue.
I've taken a few pictures here -
View post on imgur.com
and honestly, they look fine. Thus, I presume it's the bottle that's gunked up, but how do I easily remove it for cleaning? If I'm able to detach the hose at the bottle end, should I use a wet vac, or do I use an air compressor to blast air through the hose? I don't want to damage anything with compressed air.
Regarding the washer fluid, I have just got the washer fluid low warning, so that seems to be working OK. That's really disappointing with RainX, I used to put them in my past cars, but not the BMW
Many thanks in advance!