What do you mean by farming land? Pretty much all non-urban “landscapes” in the UK are farmed to some extent – with the exception of forestry and some estates managed for shooting (many of these are “farmed” too), and some other exceptions where it is a little more blurred.
If I was bivvying/camping anywhere near a house or habitation and thought there was a possibility it might be a problem, I’d ask. The only problem I’ve had in the past is more along the lies of “oh, come in- d’ you not wanna stop in the byre/on the lawn…”. Though I’d imagine this might not be the case in some areas.
As above, generally speaking, pitch at dusk, out of sight, leave no trace and be moving on by dawn. Don’t camp amongst stock or in crops. No fires where you will damage rocks or soil (so often a no-no). No washing in watercourses. No crapping all over the place- burn toilet paper, dig a small hole to bury any waste. Carry away everything you carry in. No camping or bivvying alongside routes/tracks/paths is often a maxim for some, but IME this varies on where you are.
