SELECT I.UnitId
  FROM #Inserts AS I
  WHERE NOT EXISTS (
    SELECT 1
    from   #Inserts AS INS
    INNER JOIN Organisation AS O
        ON INS.OrganisationId = O.OrganisationId
        AND INS.UnitId = O.UnitId
    )

DELETE INS FROM #Inserts AS INS
  INNER JOIN Organisation AS O
        ON INS.OrganisationId = O.OrganisationId
        AND INS.UnitId = O.UnitId

SELECT I.UnitId
FROM #Inserts I
WHERE NOT EXISTS (SELECT 1
                  FROM Organisation AS O
                  WHERE I.OrganisationId = O.OrganisationId AND I.UnitId = O.UnitId
                 );