I think I would go with Common Darter nymph,
Sympetrum striolatum. (Sorry to add a third possible ID to the list!)
The species is common in Ireland as well as England and Wales; and the short, broad body shape and wide head look right.
I find this guide to dragonfly nymph exuviae useful:
http://www.uksafari.com/jpeg2/dragonflyexuviae.jpg
There is a nice clear photo of a darter nymph at the following web page (you do need to scroll down a little):
Neil - pond dipping - Common darter dragonfly nymph and great diving beetle larva