Lesser Black-backed Gull

You are right zhabiz, the color of legs is very important, and when rounded of to Yellow Legged and Lesser Black Backed, I suggest latter as the color of wing might give us hint, Its darker grey. Also, I feel the last bird is Yellow legged Gull, I feel it is lighter grey in color compared to first three pics with rest everything same.

If they are going to be classified, they might as well be classified right! So sometimes a little arguing is a good thing!

Even though I suggested the Great Black-backed Gull, I tend to agree with the speculation in your notes that it is the Lesser. After posting, I noticed that the legs were still not right to be the Greater. Great spotting, in any case! :^)