But a legitimate BBC Sherlock plot idea just freaking exploded in my brain, and the bunnies are closing in as we speak.
Okay, Self. I know you have a bad history of jumping ship when a new fandom catches your interest. But it hasn't happened in years, ever since Doctor Who became your One True Fandom, despite discovering such things as the new Star Trek, Dexter, the Mentalist, Iron Man, and Buffy the Vampire Slayer (you always were late to the party, Self). So there's no need to panic. In fact, let's consider this a good thing. Writing anything is better than writing nothing and I still badly want to work on the Doctor Who stories I never got a chance to finish so if I can get back into the habit of writing at all it's a Good Thing.
So stop overreacting and hyperventilating. You're not cheating on your One True Fandom just because BBC Sherlock is slowly taking over portions of your fic brain. You can write the idea down in a shiny new BBC Sherlock plot bunny pen and let it gestate for a while as you finally get to make more progress on those Doctor Who stories you've wanted to work on again for positively ages.
(But it's about his violin, the music and sounds and physical techniques and mental agility and emotional expression of which I know so intimately because I've been playing it myself for so long. In so many ways it's a puzzle, a challenge, a distraction when you just need your brain to shut the hell up for a while...)
Crap crap crap. I'm going to go play my violin for a bit and then go to bed, and hopefully I will wake up saner tomorrow.