Ok so I checked the starter connections and as dave thought the red/black thin wire was on the wrong bolt (one on the top nearest to the block) so I swaped it onto the bottom one. I then re-checked the readings on the multimeter and they're the same as before, I'm still getting a 12v reading off the blue/black in all positions
Out of curiosity I did connect the loom up to the battery negative and try checking the dash again and I do get one light coming on now (oil pressure I think?), the fuel gauge drops to zero (was previously showing full), and the water temp gauge goes up slightly by 5mm or so. Any idea's what I can try next to work out what's wrong?
