Because I am sad I have spent hours today compiling statistics*.
For 2012 Olympic medals, Uk athletes, I can track down so far:
Equestrian: 1 medal event: 1 team of 5, all private or probably private
Cyclists: 4 medal events: 1 mixed team gold, 1 foreign educated, 1 ordinary comp, 1 grammar
Swimming: 2 medals: 1 state; 1 ?
Shooting: 1 indie
Rowing: 6 events: 1 pr all indie; 1 quartet of 3 grammars+1 indie; 1 octet: almost all indie, 1 state 3 ?; Watkins-Grainger pair both state; Alan Campbell same Belfast grammar as others!; Natch+Sash both indie
Men's team bronze in gymnastics: 5 athletes of which 2 comp, 2 ? and 1 mix of comp + HE
Canoeing: 2 team awards, 4 athletes: 1 indie, 1 state, 2 ? (2 mixed teams)
Judo: 1 state
*Actually it's quite interesting how people got into these sports, plenty of them didn't get into rowing-shooting-whatever until University age, anyway. Except for rowers, there's not many at Oxbridge, too. :)