BHX is one diversion point according to a CAA A380 airfield diversion compliance letter I read last year. Code 'E' runway and taxiways etc but obviously only as a fuel or emergency diversion as cannot take off fully laden on the existing runway. Maybe after 2012 though when the extension is built?
So I guess most of the other major UK airports fall into the same catagory.
Im not sure on SIA's existing diversion points, but as a guess they are probably airports that are huge or are already handling A380's so will have all the necessary kit ie AMS, CDG or FRA.