Green caterpillar/larva - appeared to be eating reed leaf (second picture on bramble branch - fell on branch from reed leave when I moved reed to take a better picture)
Approx 30-40mm long
No interactions present.
Caterpillars have up to 5 pairs of prolegs and sawflies have 6 or more pairs (if I remember correctly). I think I can see 6 or 7 pairs in your photo.
Lat/Lng: 51.475468, -0.235766
OS grid ref: TQ226766