I've lived in this place on the South Wales coast, a little inland, for the past 20+ years. There's always been a large colony of the common type of gull living nearby. Someone maybe stopped feeding them recently (past 2 years) as they now perch on our house, and generally come a lot closer than they used to. There are many hundreds of them, which you can plainly see when they do their mass spiralling. I find their calls, especially when they're all at it at once, deeply affecting and lovely.
So something has changed, for sure, but I can't say what. The impression of there being more in my neck of the woods might be because colonies from elsewhere can't find food so have moved here ๐คทโโ๏ธ .
Also, what was that in the video about sand-eels not being fished any more?