A book that I speak very highly of (it's answered so many of my rabbit questions in the time I'v had Dex and Lily I wouldnt be without it) suggests that if 2 rabbits can not tolerate each other to put both rabbits in a cardboard box and take them for a car ride.
Being slightly scary for the rabbits, they should concentrate more on keeping their balance meaning they can not adopt the aggressive body language. Once back from the drive, split the pair immediately. Each time you take them for a ride, leave them together longer and longer, return them to neutral territory and try again.
Once the sessions in neitral territory goes well, gradually increase the duration, as ratty_ratkins suggests, and try feeding the rabbits together. One they are comfortable in neutral territory, move it along to their familiar surroundings.
I appreciate you may already have tried simliar techniques, I just thought i would offer a possibility - I'm sure you're pretty frustrated, not to mention upset.
I wish you luck. (I alsi realise have just realised that you if you haven't got a car then it may also not work!!!