11.57V drops to 8V at the coil when cranking with plugs out. Guessing it would drop even lower with them in.
Only me so can't check it at the battery when cranking.
Why not? You don't have alligator clips? You need to get some.
How exactly are you cranking the engine?
If you are checking coil voltage by jumpering the starter relay, this does NOT activate the coil bypass circuit. You MUST check cranking coil voltage by USING THE KEY to crank the engine.
This is because when doing so, the "run" circuit goes cold, and the coil bypass circuit supplies power direct from the key. That circuit may not be working.