No interactions present.
Just came across a picture of an Anopheline mosquito pupa in a book and it is very very similar to your insect above. So much so I think its a better guess than the chironomid I have suggested previously (they are similar looking but chironomidae pupa have smaller thoracic regions in relation to the rest of the insect).
Can you give an indication of size?
Lat/Lng: 51.8, -0.9
OS grid ref: SP8112