Driving through the outer parts of Sheffield today three of us saw a pair of gull-like birds in terms of size and shape (larger than a wood pigeon, with pointier wings). We think their bodies may have been a pale grey colour but their height made it difficult to say for sure, but the striking think was underside of their wings was clearly pink.
Welcome to the RSPB Forum I have to say your description brings up of many thoughts of many bird species makes me think of Terns for some reason but they are not city dwelling birds No doubt someone else will come up with other ideas.
Regards
Kathy and Dave
In reply to Cjdales:
Richard B