Doc says could have low grade lymphoma, wide spread persistent nodes but all cm or less, too small to biopsy, bloods ok, well, is there any benefit to early diagnosis if they might just observe initially anyway?

It is not feasible to provide a meaningful opinion without additional history, physical examination and may be some tests. You may feel the nodes every couple of weeks, if any of the lymph glands doubles in size, becomes painful, ulcerates, or other nodes become enlarged, or you develop fever, or lose weight, you should see a doctor. Wish you good health!