Floating leaves are Potamogeton sulcatus, but the inflorescences held above water level are Potamogeton ochreatus (leaves visible in water). Inflorescences of Potamogeton ochreatus have gaps between individual flowers, are spaced out, those of Potamogeton sulcatus are solid no gaps. Could be worth separating the photos into two species.
Hollows are in tight demand! I actually wondered if this was not the Stevie pair's daughter from two years ago, as I've seen the same pair visit the hollow previously, but not be moved on by the pair. And in the evening, I can hear one pair in the branches above the hollow, and see the Stevie pair - and they just gently chat to each other