I went to that exhibit when I was in Cardiff last September, and hope to get there again this year. Maybe by then they will have some stuff from the new series. Did you explore the area around Cardiff Bay, i.e. getting a photo of you on "that" stone by the water tower

and seeing other Torchwood related sites?
BTW, for those who might have seen reports that Matt Smith will be leaving after this series, bear in mind that the source of that article is The SUN, Britain's version of the National Enquirer. Karen Gillan said he wasn't going anywhere.