Under current English law if am on someone else's property and I not on CROW land or a Public Right of Way, then if challenged I would have no alternative but to apologise and politely explain what I was doing there and ask if I may continue. I am too good a navigator to plead igonorance. If I am refused permission to continue then I would offer to leave. There is no point in a confronation, it would achieve nothing and legally I am in the wrong.
On the other hand, if I am where I am allowed to be, then I would equally poltely point out that I had a right to be there and would endeavour to prove it with my phone, gps or map. If I was not allowed to continue then I would leave, saying that I intended to report the matter.
Bottom line, I may not like it but until the law is changed, if I am trespassing I am in the wrong amd there is no point in arguing with the landowner, better to get the law changed.