Hi, just to post followup, I let it have a week out of the cast before cycling. And cycling is absolutely fine. I was worried about the lack of forward-flex at the ankle, but it's all good.

As I currently can't stand on toes on that foot, I'm sure it's the best thing for it, as cycling works that standing-on-toes set of muscles with every pedal .

As for the rest of my general fitness, and my sore backside from the cycle seat however...

Cheers for the advice!!