  We present the optical-to-submm spectral energy distributions for 33 radio &
mid-IR identified submillimetre galaxies discovered via the SHADES 850 micron
SCUBA imaging in the Subaru-XMM Deep Field (SXDF). Optical data for the sources
comes from the Subaru-XMM Deep Field (SXDF) and mid- and far-IR fluxes from
SWIRE. We obtain photometric redshift estimates for our sources using optical
and IRAC 3.6 and 4.5 micron fluxes. We then fit spectral energy distribution
(SED) templates to the longer wavelength data to determine the nature of the
far-IR emission that dominates the bolometric luminosity of these sources. The
infrared template fits are also used to resolve ambiguous identifications and
cases of redshift aliasing. The redshift distribution obtained broadly matches
previous results for submm sources and on the SHADES SXDF field. Our template
fitting finds that AGN, present in about 10% of sources, do not contribute
significantly to their bolometric luminosity. Dust heating by starbursts, with
either Arp220 or M82 type SEDs, appears to be responsible for the luminosity in
most sources (23/33 are fitted by Arp220 templates, 2/33 by the warmer M82
templates). 8/33 sources, in contrast, are fit by a cooler cirrus dust
template, suggesting that cold dust has a role in some of these highly luminous
objects. Three of our sources appear to have multiple identifications or
components at the same redshift, but we find no statistical evidence that close
associations are common among our SHADES sources. Examination of rest-frame K
-band luminosity suggests that 'downsizing' is underway in the submm galaxy
population, with lower redshift systems lying in lower mass host galaxies. Of
our 33 identifications six are found to be of lower reliability but their
exclusion would not significantly alter our conclusions.
