simbrooks:BSAC and DAN both seem to put out stats, i dont know how detailed these thigns are and whether they can really help improve the way we all dive - if they are too general or not.
The BSAC one covers all known/reported incidents in the UK (all agencies) and all BSAC members that have incidents abroad.
The UK ones are compiled via reports from the media,coastguard, police as well as the ones officially reported to them so is fairly comprehensive, chances are if any official service was involved in some way it'll be included. As for how detailed, you can see for yourself as its on their site.
DAN i dont know about (i) because its not as popular or commonly consulted here and (ii) i think you have to be a member to get them.