Just an update on this...
This is a multi tenant database design. What I found after experimenting was that if I logged in just as admin with administrator rights I could see the list ok and also as a drop down list on the farm records. So I disabled the business rule which is recommended if you watch the multi tenancy video in regards to restricting access to records that dont belong to the particular company you are working in.
if LoggedInSiteUser.ob_Site.ob_Company<>Agronomist.ob_Company THEN READ PROTECT Agronomist FROM ALL EXCEPT Administrator
Once I disabled this they all appeared in the query list and the Farm record reference dropdown link. The interesting thing about this is that all my other codesets use the same restriction rule methodology and they all work fine as expected. So there are 2 distinct aspects to the Agronomist records that set them apart from the other codelists...
One is that they have a Peer to Peer Reference relationship with the Farm records. No other codeset list has this sort of reference connection.
Second, the Agronomist object is set with a Communication Channel of type Email so we can send reports to them about Farm Treatments.
So the question is and I guess Aware Support are the only ones who could confirm this - would either of these conditions cause a block on the access level interrogation of the object?