If you are carrying out a pfl into a field, you can goto the deck as long as you have a clear overshoot to keep in rule 5. The CAA would not take any action if it was in the benefit of flight safety and pilot training.
Obviously, avoid tractors, footpaths etc. but a one off pfl isn't going to cause an issue if you are sensible.
Landings are exemt rule 5. How can you land otherwise or take off. Now a flyby is different. You need permission to break rule 5 from the CAA and a flyby is not a take off or landing, but prove a low approach and go arround wasn't a training exercise in approach perspective - or a lesson in FLWP (runway inspection prior to landing). The last of the three inspections is at approx 50' prior to landing. And this can be done off airfield.