Exporting the GMFs from the HDF5 is highly nontrivial, since the correspondence between GMFs and sites is coded in pickled objects stored inside the HDF5.
We plan to improve the situation in the future and to make available the information in a clean way, however this will take some time. My advice for the time being would be to export the csv and than bulk import it, without interacting directly with the HDF5 file. At the moment the structure of the HDF5 file is highly volatile and subject to change, the CSV exporters are in a better shape, but still subject to change, only the XML exporters are stable.