It is obviously a very overcast day - i.e what they call a normal one in Dundee.
If i was walking past i would dismiss it as an LBB on size, structure and plumage but we shall have to agree to disagree:t:
It looks like an adult Lesser BB with its Winter-head plumage. It is slightly smaller than the adjacent Herring which they are. Yellow-legged are are more ‘brutish’ looking and usually sport a bill to match. Adult YLG often show a White head in the Winter not the streaky-Brown of others.