As I said, not a lawyer, but.....
Presumed liability would come into play in a civil action when one person is injured and wishes to claim a remedy from the other. In a pedestrian/cyclist crash, if the pedestrian isn't injured there are no grounds for a claim from them.
I can imagine 4 scenarios where one or both might be injured:-
1) The cyclist was where s/he shouldn't be - on a footway. Pretty clear cut, the cyclist will be liable, and the pedestrian could claim for any injury, whereas the cyclist (if injured) wouldn't stand much chance at all.
2) The crash took place on a shared path (segregated or otherwise). Although the cyclist is entitled to be there, s/he is expected to cycle carefully around pedestrians, so again I would say clear cut, the cyclist will be liable for any injury to the pedestrian but not vice-versa. I think the cyclist would have to show that the pedestrian deliberately and knowingly ran into them with no possibility to stop. A tall order.
3) The crash took place on a road (whether or not the cyclist was in a cycle lane on the road). The presumption is that the cyclist would be liable, because the cyclist should be looking out for pedestrians absent-mindedly walking in the road. I think the cyclist might be able to reduce the liability or transfer it entirely to the pedestrian if s/he can show the pedestrian's action was so sudden and close that a collision was unavoidable. This assumes the cyclist was not riding too fast or too erratically in the first place. eg. if a cyclist went through a green light and a pedestrian stepped onto the road at the last second, I think the cyclist would probably avoid liability, and might even succeed in an action if s/he was injured in the fall.
4) The crash took place on some infrastructure dedicated to cyclists and only cyclists. I'm not sure such infrastructure exists in this country, but if it did, it would be easier to transfer liability to the pedestrian and claim damages if the cyclist were injured.
Having thought through this, it does seem as though the cyclist would normally be liable, but that's how it should be.
Where does this leave the Barnton path situation where a darkly clad pedestrian can't be seen in the pitch dark? Should the cyclist proceed at walking pace, or should the Council be sued for not lighting the path?