Thanks for all who responded. The list is not too busy so thought I should feedback:
Michael's analysis was spot on. My seed hole on the outer ring had Length not Diameter reference.
When that is fixed, the hole circle diameter can be called up by Show - Feature & View, click (interestingly) any hole (not just the seed) and remove any spurious other dimensions (like the hole diameter that is in the callout note) using Keep Selected on the pitch circe dimension.
Best wishes
John Prentice