Here's the area in question under the microscope.
I need to bodge this capacitor between the two vias at the south side of the WLCSP (U26) at the center of the image, in the gap between it and C154 (a massive 0805).
It's an annoying angle but I have plenty of space. I might almost be able to fit an 0402 in there if I tried hard but let's see what the 0201 does first.