Interesting case. If possible can you attach some x-ray images for us to take a look at?

You are early post fracture and you are perhaps showing non-union. Therefore the idea of muscle strengthening should be taken lightly. Also I am not sure how one can be partial weight-bearing but still be instructed to increase as much muscle strength as possible!

On the bike; although the pedals move there is a 'sort of' of base at both ends of the lower limb movement (seat and foot) and the movement is what we could consider somewhere between an open and closed kinetic chain. Swimming is an open chain where to foot end is free to do what ever (rotate/twist etc) and therefore is a lot more demanding on the leg and the fracture. I would suggest only crawl (freestyle) be done at this stage if you are to swim.

Perhaps you need to discuss more clearly with the surgeon what you can and can't do at this stage. Bone stimulators such as magnetic fields are useful in stimulating fracture healing but there's not to many PT's out there who have one.

In terms of time on the bike that is also hard to say. I would work to a plan of starting out for say 5 mins and repeat daily for a few days before increasing. You need to look at the afteraffects both immediately and cummulatively over a few days before increasing the time spent. Any cramping in the muscles or numbness could be an indication of fracture movement when riding so I would be careful and I would again consult directly with the fracture clinic if in doubt. Seems like you could really do with a private Physio consult if the NHS is taking to long.