If you are asking whether or not it is a Grey-headed Gull (Larus cirrocephalus) then it is. If you are asking to confirm the subspecies, then I don't think it's possible to tell the subspecies apart visually, however zootierliste doesn't list any of the South American subspecies in Europe.
Thanks LD - I had it as African on my notes taken from the signage, but as my bird ID's aren't brill I wouldn't have put it past me to have taken note of a different gull to what I photographed