Think I'm a bit late to this thread, but ah well.
I just had a look at Clarence Dock, The Tannery and Leodis today. Wasn't keen on the Tannery - the rooms were pretty small, I found it a bit claustrophobic and I didn't like the surrounding area much. Now, I'm totally stuck between Clarence Dock and Leodis (which I was even before I went to see the accommodation!).
My only worry with Clarence Dock is that it's so far out. If I could be assured that it wouldn't have an effect on my social life, that would definitely be my first choice. Leodis is much closer and was still nice, but I've heard it's supposed to be quite oversubscribed and I'd rather have the smallest possible chance of being put somewhere other than my first choice. However, Clarence Dock seems to have a lot of interest this year - so maybe even that'll be oversubscribed!