I'm perfectly certain you're correct, Steve. My father worked for a large company and when Lord X decided it was time for his son to join, he asked my father to tutor him, show him the ropes from the ground up. It worked very well. In Jeremy's case, possibly -because of his adoption?- he felt unworthy and of less value than the paid employees?
I think he will have had some type of preferential treatment. But more probably along the lines of having days off when he wanted or not working late. ( Nevill stated he had trouble getting Jeremy to work weekends ) Which means he wasn't that forceful with him otherwise he would have made him do so!
I definatley don't think his duties were just farm labouring. One employee in his statement stated he would go to Jeremy to receive instruction, and farm reps at the trial said " they found Jeremy the easiest person to deal with out of the family " which meant Jeremys duties would have extended somewhat than just a bloke in the fields. Having said that, labouring duties did make up time in his job as he was on the tractor and fields. Nevill himself did these tasks ( and he was the gaffer!
Having said that there is a source of Nevill saying Jeremy was shaping up well at the farm. Believe Jeremy would have got into it but knowing his character he probably wanted things done his way. Didn't he have plans to computerise the place and only half jokingly suggest they make Barbara Wilson redundant?