No personal experience I am afraid as I am only 6' 2" but I have several tall friends, although not as tall as you.
A friend of mine rides a GIANT (slightly ironic) xl frame (can't remeber the model but I can find out if you want) which fits him quite well. He is "only" 6' 7" and looking at him on it I am not sure that it would scale up that well to someone 6' 10". Another mate who is 6' 4" has a custom BJ and rates that, not really tall I know but tall enough to have some difficulty in finding frames. Lastly my cousin is about 6' 6" and has found Cannondale frame that fits him, I can find out more if you like. I think all of these guys where on the edge of what the biggest production frames could be made to fit tbh.
If I were you being as you are in Eire I'd go semi custom / custom with a British frame maker and use the power of the Euro.