The coil is getting hot because there is a supply to the coil and current is flowing through the coil all the time, even after you have tuned off the ignition and removed the key. Not a good thing and could eventually cook the coil.
A couple of possibilities:
1. Faulty ignition sw that is not turning off
2. Connections at ignition switch are wrong. Main incoming supply connected to IGN ON side of switch????
3. Tacho is faulty or not wired up correctly and is bypassing the ignition switch.
You need to check wiring connections at ignition switch and test to see if ignition switch is actually turning On and OFF.
Tacho not working could be faulty tacho (there are 2 types of Clubman tacho, a current sensing type and the later voltage sensing type) , faulty or wrong connections, or maybe the flexible printed circuit board on the rear of the instruments is faulty.
The 2 problems could be related or completely separate. (Faulty tacho could be supply current to the coil, bypassing the ign sw.)
Just curious. If the ignition won't turn off how have you been stopping the engine? What is cleaning up some wiring?
This will give you a start.
Regards
RonR