The Highway Code puts a duty on both road users to take extra care and look out for pedestrians, and equally for pedestrians to be aware of road users. As a pedestrian, you should treat the driveway or entrance as you would any junction or crossing. Look both ways and only cross when it is safe to do so. This is the best course of action to take for the sake of your own health and safety.
Road users should take extra care when navigating entranceways and driveways and keep a constant look out for pedestrians who may cross. Drivers should edge out (or in) very slowly and keep both hands on the steering wheel to maintain full control, and constantly look left and right to spot any oncoming pedestrians. It goes without saying that when reversing in to an entranceway or driveway, even more care needs to be taken. Keep to a very low speed, never make any sudden movements or rev the engine if the pedestrian is crossing slowly, and check all mirrors and look behind you carefully.
^^this is what we were taught as children. Pedestrians cannot absolve themselves of all blame, the driver would have been at more fault if they had reversed unreasonably quickly out of the driveway that a pedestrian didn't have a chance to see they were coming, but for your own sake you should always be paying attention ehen crossing drive ways.
The Highway Code also says
Rule 15
Reversing vehicles. Never cross behind a vehicle which is reversing, showing white reversing lights or sounding a warning.
If you were paying attention you would have stopped for the car.
If your dog had been injured 100% your fault. Hope you learn from this and stop using the extendable lead where you are risking your dogs safety.