I'm surprised that DN won't come to your house, Simon. Perhaps the "system" doesn't realise about your mobility problems? DN may be able to change arrangements when you reach. However, whatever you do, do get wound & dressing changed when you were told to - not wanting to scare you, but if it goes wrong at the beginning, your foot might never recover, leading to further problems. Good news, of course, is that you say your calf is feeling better, so you may actually be able to walk further now than before op. Do you have any walking aids - sticks or crutches? If you need them, then phone GP or surgical team who did op to arrange, as it's important that you get measured and shown how to use them properly.
If you can't walk all the way to GP surgery to get dressing changed, is there a bus for at least part of the way, which would be cheaper than taxi?