So by some massive weird coincidence I was reading the Discord earlier and saw D0pefish was talking about how easy it was to brick your Pi 3 by shorting something, and I was like "ooh didn't know that, need to be careful...
Now less than 8 hours later after putting it in a new case and reconnecting everything (and I know I messed it up because I wasn't concentrating I am getting nothing on my MT32-Oi display and after a few seconds of blinking leds the Pi turns it's lights off. Tried re-doing the SD card but does this sound I've burst it?
Wil try it with a proper Raspi image and a HDMI cable tomorrow but I'm annoyed with myself here.