A landowner/farmer shouted at me for walking on his land – is this allowed?

If you were using a public right of way, then no one should dissuade you from using it. This type of behaviour is intimidating to users of the right of way and should be reported to the highway authority. If you are unsure if you were using a public right of way you should check with the surveying authority (county council or unitary authority) to find out if the path is marked on the definitive map.