In reply to DavyWA: I don't have a Fitzroy so can't compare, but I do have a RAB Photon (they have a bit more insulation now than my one does from two years back), a Haglöf Barrier and a TNF Redpoint Optimus. I can say that the Citadel is very noticeably warmer than the other three (same is true of my DAS). For most of the year this might be overkill - but for long belays midwinter - it's marvellous!
So whether you want to go up to the Citadel over the Fitzroy might depend on where and and when you climb (how long you have to belay for) and whether you're happy with weight in return for lots of warmth.
Check out Dan's review of the Fitzroy if you haven't already:
http://www.ukclimbing.com/gear/review.php?id=4457 interestingly he was wearing those weight of jackets whilst moving sometimes. It would have to be pretty terrible conditions to actually climb in the Citadel in my experience!