Sorry if this appears basic!! is a person on a dependent's visa with no recourse to public funds entitled to claim child benefit?

No. Child benefit is one of the public funds benefits. And see section 115 of the Immigrations and Asylum Act 1999. This lists a number of beenfits (of which child beenfit is one) that cannot be paid to a "person subject to immigration control". One of the categories is a person who is not an EEA national and has leave to enter or remain in the UK which is subject to a condition that he does not ahve recourse to public funds (subsection 9 (b))