First I need to know how its wired.
Are you using the stock ECU? It's definately related to the coils,
and there's only two things needed for those to work (well, 3 if you
count energy). you've got your connection of four wires to the Crank
Angle Sensor, they connect directly to the ECU (There's one connector
in there, but the wires are straight runs), and then there's the
connection to your coils.

Your trailing coil has 6 wires going into it. two Black/Yellows, get
12V directly from the main relay (which gets its power directly from
the battery), and three wires going to the ECU (Blue/yellow,
Brown/Yellow, and Blue/Red). The remaining wire (Yellow/blue) is the
wire that runs your tachometer, and it connects directly to your gauge
cluster.

Your leading coil will only have two wires going into it, one
black/Yellow (Power, just like with the trailing coil), and your
Green/Yellow that goes directly to the Ecu. If all of these wires
are good (pay careful attention to your wires goign to the ECU, check
contiuity between the coil and the ECU), check the grounds. Coils
ground through the metal bracket that they're mounted to, the one that
gets screwed down to chassis. If that is loose, or just screwed down
onto paint, you may have to sand that a bit, or tighten it up.

Hope this gets you on the right path All of the information i
taken from the Factory Service Manual (which I'm sure you have,
right?), The 50_wiring_diagram section, page 50-28. I also had a
bit of a wiring nightmare with mine, when I made my own wiring harness
to run it from the Megasquirt. It's a lot easier if you can deal with
it, one system at a time
Send me over some pics of the MG, I love those cars, and I've always
wanted to drop a rotary into one.

Oh, hit me up on AIM if it would be easier.. My AIM name is GreatLeper

Good luck!
~Wonko