  Accurate and precise radius estimates of transiting exoplanets are critical
for understanding their compositions and formation mechanisms. To know the
planet, we must know the host star in as much detail as possible. We present
first results from the K2-HERMES project, which uses the HERMES multi-object
spectrograph on the Anglo-Australian Telescope to obtain R$\sim$28,000 spectra
of up to 360 stars in one exposure. This ongoing project aims to derive
self-consistent spectroscopic parameters for about half of K2 target stars. We
present complete stellar parameters and isochrone-derived masses and radii for
46 stars hosting 57 K2 candidate planets in Campaigns 1-3. Our revised
host-star radii cast severe doubt on three candidate planets:
EPIC\,201407812.01, EPIC\,203070421.01, and EPIC\,202843107.01, all of which
now have inferred radii well in excess of the largest known inflated Jovian
planets.
