I am not sure how you know they are from the UK. Maybe I do not know my way around Youtube enough to find out where they come from, but I have had a couple of dislikes, posted anonymously...could be from anywhere in the world.
Would it not be a good idea if users could only post dislikes in conjunction with a comment. This would help the cause of constructive rather than destructive criticism, and would identify the critic. Clearly, disliking without commenting is cowardice.