I am presuming that if you remove the dizzy cap, you shouldnt be able to turn the rotor arm around with your little finger??

Just checking im not going mad??

 

nah mate some thing wrong get the dizzy out

 

Sounds like dizzy drive shaft has problem or the rotor arm has worn away and hence not sitting on drive shaft tightly.

 

It's not going to help running that's for sure!!
Hopefully it's just something silly as suggested ie broken bit inside rotor arm, and not something more serious.
They often, on most fords have a slight "wiggle" as the rotor arms are not the tightest fit on the shaft on some, so just pack a thin bit of paper there if this happens, as a wedge between arm and shaft.
tabetha