Just to make you aware Tom, the firing order is 1-3-4-2, not 1-2-4-3 - you're looking at the rotation the wrong way.
Glad you've got it sorted, chances are the misfire was caused by having leads 1 & 2 swapped rather than the lead for the Hall Sensor dangling.
If the rotor arm broke that easily during removal, it wouldn't have been long before it broke in service, probably taking the cap with it. Looking at that cap, that would have probably done you a favour though!
Little tip for doing the exhaust - don't do the nuts etc up tight until you've got all the new parts it needs fitted, then work from the front to the back, preferably with the engine idling so it's warming the exhaust up while you do it.
Not only will this make it easier to get them as tight as they need to be but also take into account the expansion of the joints and makes sure that once you've got a joint tight enough to not blow when it's warm it won't blow when it's cold and won't blow on the MoT ramp either.
