"I often find that answers are astray by 1 degree or 1 knot. I know that is irrelevant in the real world but it seems that accuracy is essential for the PPL ground exams"
For my exam I think there was more leeway than that. After all the wind direction and speed aloft is not accurate to that degree is it? If it's multiple choice I expect you will see the answers differing by more than 1knot/1 degree. I suggest you strive for reasonable accuracy but don't sweat over it. do lots of practice calcs and you will be fine.
Cheers