Chris,
I had exactly the same injury on the same leg at the start of 2003 .... 3 week before I picked up my new 749s
I did try to ride the bike but with my toes sticking out in the cold and trying to hook the heel of my plaster cast under the gear lever to go up gears was impossible.
I had about 14 weeks in plaster and physio 3 times a week for a further 12 weeks, still difficult to ride during physio. 1 of the problems was getting on the bike, at one point all your weight is on your left leg as you pivot around to get on your bike.
The good news I can offer is that if you stick to the physio and do all the exercise you can get back to 99% as before. 2 years down the line the only problem I sometimes have is a little cramp in my calf muscle on a long ride, especially if you tend to ride on the balls of your feet.
All the best and hope it works out for you.