My mainspring has a stud that the drawband hooks over.  Yours seems to have a hook on it?

komputerized wrote:

Back again...I seem to have encountered another problem. My suspicions are confirmed - I've definitely done something to the mainspring. Whichever way I turn the drum, there's no tension, it just clicks as I turn it and stops wherever I leave it, ie it doesn't spring back into its normal position. Am I well and truly stuffed? 

 

Nah, just remove the drum and pop the top off of it.  It likely came unseated.  If the spring snapped, take a photo of it and we’ll go from there.