As far as the E91 is concerned:
Open the glovebox
On the back of that there are two 1/4 turn fasteners.
Undo and remove the back of the glovebox (the bit facing front, if you know what I mean!)
In there will be a plastic card with all the fuse numbers and locations.
Look for the headlight washer symbol.
Look again into the glovebox, and in the space you've uncovered, on the firewall, you'll see the fusebox - you may need a torch, but the glovebox light does illuminate it a bit.
On mine, fuse 48 is on the right, half way up. Use the red removal tool, as there are wires that get in the way otherwise.
On my plastic card, fuse 48 also has a windscreen washer symbol, (it's got 2 entries for fuse 48!!) but when I remove it, only the headlight washers stop, everything else works OK.