Hi Steven ..
Being so new to the Forum .. I'd hate to thought of as being pedantic .. but there's no such thing as a "Seagull" (check your Field Guide) .. There are many different species of Gull .. eg .. Great Black-backed, Lesser Black-backed, Herring, Iceland, Black-headed, Ross's, Yellow-legged etc ... the term "Seagull" is guaranteed to have any Birdwatcher tearing his (or her) hair out in clumps .. :lol:
The great pictures you posted suggest to me a juvenile Glaucus Gull .. as borne out by the following link
http://www.rspb.org.uk/wildlife/birdgui ... /index.asp
Bye for now ..
Kev ..