Training around a back injury?

29/female, planning to do a couple of sprints next year and have an entry for the olympic distance London Triathlon for August 2014.

Was purely a runner until 2012. Took a heavy fall during a half marathon, got back up and finished that race, but have had a lot of issues with my lower back and pelvis since then which have seemed to be stubbornly resistant to physical therapy. I was at a physio fortnightly for about 6 months after the original injury and got to a stage where I felt around 75-80% recovered, working with a good ashtanga yoga instructor brought me to about 90%, but then I moved country and lost that, and am still having all these issues again.

Of the triathlon disciplines, I now find swimming to be the most comfortable of them (and developed a love of open water this summer), and my running has been the most affected by the injury. I used to be able to run a 48-50 minute 10k/1:50 half/4 hr marathon, but I'm back to being able to complete a 10k in 60-65 minutes at a struggle. I'll probably need to be able to do most of my aerobic training on the bike.

Basically, I need some hints on strongly swim/bike-focused training, with a max of 2 running sessions a week.