Local magnetic interactions in lanthanide compounds have recently been shown to tune their entropically driven magnetocaloric effect (MCE), useful for magnetic coolants. In this regard the LnOH(CO3) (Ln = lanthanide) frameworks are particularly interesting as they feature the highest MCE performance and TbOH(CO3) and DyOH(CO3) have recently shown enhanced properties above 4 K for in modest magnetic fields; potentially making them more useful in practical cooling devices. We will probe the magnetic correlations in several members of this series to understand the differences in their MCE through analysing their magnetic diffuse scattering. This will establish the relationship between their magnetic interactions and MCE, enabling rules to be established for optimising performance. This requires high quality neutron diffraction data ideally matched to the unique capabilities of WISH.