No interactions present.
Yes, Shrike2, you have convinced me. Also there was quite a number of these hawkers about whereas Southerns are apparently more solitary.
The visible features confirm the ID:
Southerns have broad 'antehumeral stripes' (the stripes on top of the thorax) and bars of colour on the last two segments of the abdomen.
Migrants, like this one, have short, narrow antehumeral stripes, and clearly separated spots on the last abdomen segments.
Lat/Lng: 52.749, 0.078
OS grid ref: TF403188