Creeping plant with red stems and opposite leaves.
No interactions present.
Thanks for the IDs, I am not familiar with either of these species. I don't think it is Lythrum portula as this has flowers in the axils and the remains here were definitely on stems. Will make a point to check again later in the year. Interestingly it is a calcareous woodland, must be locally acid here for Hypericum humifusum to grow.
Lat/Lng: 50.7, -1.3
OS grid ref: SZ5292