It's are, I believe, because even though Coldplay is not a pluralized noun you still treat it as a plural noun. eg "deer are" vs "deer is". Even though "deer" is not pluralized it's still a plural noun.
The language allows you to go either way on that, depending on whether you are referring to them as as individuals in a group, or to it as a single unit.
In this case, the meaning is something along the lines of: "the individuals in said group are together called 'Coldplay', which is a British alternative rock band."
It is a little jarring on the American ear, because of the juxtaposition of plural and singular referents that both indicate the same signified object -- a linguistic faux pas, if you will.
I suppose it is something used in the same was as things like "give it to Jane and I," by the simple masses who think they sound smart. (The indirect object is "to Jane" and "to me", which is "to Jane and me".)
I cannot speak to usage in the UK or other areas, but I suppose that even in the UK it is a bit of a regional thing... (I could be wrong though).
When I think of bands I always think of them as single entities, which is the source of my frustration. Grammar was drilled into my head I think more than some, because although I also had (have) grammar in school, I did a lot of reading (which I suppose isn't uncommon(although I tried to read the dictionary I ultimately gave up))
When I was a kid I would read the World Books Encyclopedia...My teachers always laughed..until they realized I had gone through all 22 volumes in my last 3 years at that elementary school. Yea... I was such a knowledge hungry little prick :P
It is a little jarring on the American ear, because of the juxtaposition of plural and singular referents that both indicate the same signified object -- a linguistic faux pas, if you will.
:S
I used to read the dictionary and grammar books as a kid. (Quite often for fun.)
I never read the dictionary, but I did read grammar books (mostly stupid stuff like "How to use capital letters").
I have never any reading done, but I good grammar think can do.
Speaking of which, why the heck can no-one type correct English, I mean is it really that hard? I am not even asking for commas, just correct spelling, and maybe a capital letter.