Finally managed to track down the identity of the 'mystery figure' - was looking at the Mega-Minis site as suggested by Jagatai (thankyou) and in a round about way decided I was looking for a Barbarian of some sort. To cut a long story short I found the Lost Minis website and searched for 'Barbarians' - first thing that came up was the 'Barbarian Personalities' set from Asgard, sculpted by Jes Goodwin (who did lots of Citadel stuff) and though there wasn't a picture I deduced he was 'BP8 Aurock Storrirkin' - Stuff of Legends fortunately had pic and confirmed this:
He is the one on the bottom left. Don't know why this bothered me so much but I was on a mission to find out! I am usually pretty good at identifying old minis and was determined to track this one down! Thanks for the suggestions guys.