Looking at those pics a guillemot sounds most likely. Couldn't pick out much detail but I think the white was kept to the underbelly. There was also something nesting in the crack of The Arrow but not sure what it was. I assume these birds mustn't be on the RSPBs watch list if St Govan's and Mother Carey's aren't under the bird ban?
Was belayong Boggo the other day when he got a face full of Tawny Owl at the top of Estremo at Millstone!
Slackers isn't your "Gull" a kittiwake?
Not a sighting, but truly awful......http://www.bbc.co.uk/news/uk-scotland-13339288