I don’t think either are in any real danger. That doesn’t look like a predatory fly to me, and the beast in the red corner is a Hazel Leaf-rolling Weevil (Apoderus coryli).
It’s a common weevil, and we have lots of hazel coppice so everything fits and for once I don’t think there is any risk of miss-identification. According to NatureSpot, the adults are only around in May to July, during which the females roll up leaves of hazel for the larvae to feed in. Still time to try and get a sharper picture therefore.
Where there’s a weevil, there’s a scientific study, in this case by Jaroslav Urban in 2014. For those of you who don’t subscribe to the Mendel University (in Brno) journal Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, I’ll sumarise.
The males and females consume on average 21 and 33 cm2 of leaves, respectively. The fertilized females cut into the leaf blade in an original manner, and bite into the main and side leaf veins. They fold the withering part of the blade into a short cylindrical roll. In total, they make around 30 rolls. The larvae emerge on average within 10 days. It was demonstrated that rolling of the leaves causes on average 9 times more damage to the trees than maturation feeding of the beetles.
We can probably spare that much, and they do liven the pace up a bit with their red jackets. The Swiss paper notes that they are “very wary and escape danger by running, falling on the ground, or taking off” but our friend wasn’t giving way for anyone. No one messes with a Melick Wood Weevil!