  We have studied in detail a sample of 967 SPIRE sources with 5-sigma
detections at 350 and 500 micron and associations with Spitzer-SWIRE 24 micron
galaxies in the HerMES-Lockman survey area, fitting their mid- and
far-infrared, and submillimetre, SEDs in an automatic search with a set of six
infrared templates. For almost 300 galaxies we have modelled their SEDs
individually to ensure the physicality of the fits. We confirm the need for the
new cool and cold cirrus templates, and also of the young starburst template,
introduced in earlier work. We also identify 109 lensing candidates via their
anomalous SEDs and provide a set of colour-redshift constraints which allow
lensing candidates to be identified from combined Herschel and Spitzer data.
The picture that emerges of the submillimetre galaxy population is complex,
comprising ultraluminous and hyperluminous starbursts, lower luminosity
galaxies dominated by interstellar dust emission, lensed galaxies and galaxies
with surprisingly cold (10-13K) dust. 11 % of 500$\mu$m selected sources are
lensing candidates. 70 % of the unlensed sources are ultraluminous infrared
galaxies and 26 % are hyperluminous. 34 % are dominated by optically thin
interstellar dust ('cirrus') emission, but most of these are due to cooler dust
than is characteristic of our Galaxy. At the highest infrared luminosities we
see SEDs dominated by M82, Arp220 and young starburst types, in roughly equal
proportions.
