Thanks for the help Mate.

Managed to get it sorted. Was reading on an RS for sale post that you can swap the circuit board and the mileometer over, so tried it and it worked. Just remove the 5 star head screws on the back, remove the plastic shield, carefully prize the circuit board off. Did the same with my old dash, swapped them and Robert's your mother's brother! Now I have all lights working normally, and got my genuine milage back. Just need to get the inverter sorted for the dash display now.