Chickenhouse
The UK CAA has made it clear that it will not support a prosecution of a flying instructor under Rule 5 (500 ft rule) if the instructor is carrying out training of forced landings (with ot without power) as long as resonable care has been taken to not infringe rule 5.
So I see this being if you fly less than 500 ft from a farm house you will get busted, if you fly nearer that 500 ft to some walkers who had been hidden by a hedge while approaching an otherwise empty field you will not get busted.
This was as a result of a failed prosecution of a flying instructor who was carrying EAFTO training. Any wise instructor will keep a record of this training just incase a low flying complaint is made.
UV I have known it to happen, if you get it right you just fly the aircraft out of the field so no need for any fuss, after all most grass airfields are just fields that people put the word "air" in front of to tell you that aircraft regularly use it.