So we have found the story (thanks to everyone who got back to me on this): 'The Songs start to make sense' by Vulcanlover
However the story has been taking down from the internet by its author so finding an extant copy is proving somewhat tricky. If anyone has a copy squirreled away on their hard drive I'd really love it if you could maybe get in touch with me on that. Thanks so much to everyone.
So a while ago I found a lovely if slightly disturbing fic on FFnet wherein Kurt meets Blaine in accordance to canon and starts getting closer to him. But unlike canon, in this fic Finn is (increasingly) insistent and increasingly (physically)opposed to Kurt getting closer to Blaine. Finn manages to convince the Glee club (except for Sam I think) and (for a while) Burt and Carol that Blaine is untrustworthy.
As in canon, when the Karofsky situation escalates, Kurt goes to Dalton. And Finn starts getting worse, and eventually chokes Kurt b/c Kurt isn't *listening* to him about why dating Blaine is a bad idea. Kurt winds up in the hospital with some kind of nerve damage (can't remmeber what the condition's called) and Finn is in the psych ward being diagnosed with some kind of mental disorder.
And New Directions has finally woken up to the fact that something is wrong- and it's not Blaine (but aren't being allowed into Kurt's hospital room)-
And thats as far as I read- and now I can't find this bloody fic and its driving me coo coo cachoo! Any help you guys can offer would be appreciated.