About 1.5 cm long
No interactions present.
Certainly a ladybird larva, and I agree with charlieb that it is a Harlequin, although most of the ones I see have the four orange spines in the middle a brighter shade of orange.
For more info and to report your record see the Harlequin recording scheme:
Entomologist and biological recorder
Lat/Lng: 51.604687498002, -1.2370235325216
OS grid ref: SU529898