blue in colour, visible air sack.
No interactions present.
What size was it? I don't think it is Velella - although the colour is right, the shape is all wrong. I am not familiar with Portuguese Man-o'-war, but I could be persuaded it was a rather crumpled Cyanea lamarkii.
recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.
Lat/Lng: 51.852, -5.1199
OS grid ref: SM852216