speed sensor is, as i said on the gearbox
2 wires:
a grey and blue wire
a light green and red wire
runs under the battery tray, into the fusebox, through the wing back to the speedo
the tacho on the dash (which i think is what you actually want and i misread it first time round)
has a feed from a white wire from the dizzy, this wire also goes to the "ig-" in your diag box

I hope that helps fella, apologies for my error first time round
so i would try and pick it up from behind your clocks cos you'll struggle to get it from behind the dash without removing all of it to get at the loom