The presence of a stile DOES mean you can assume right of way.

So if I put a stile in my garden that means people can wander in to it then? Silly. Not only do stiles not always indicate a legal right of way, they also don't always indicate the direction of that continuing right of way, which is the problem OP is facing. Please don't get pointlessly aggressive about this, it doesn't help anyone.

the responsibility lies with the landowner to shove up a few signs if he doesn't like people walking around the land

Absolutely not the case. 'Right to Roam' doesn't cover enclosed privately-owned farmland; you cant' just yomp about wherever you like and blame the landowner if you get caught.