  We have used several different methods (radio morphology, radio spectral
index, mid-IR to radio and near-IR to radio flux density ratios) to
discriminate between AGN and SFGs in faint, sub-mJy radio surveys. We find that
the latter two methods are the most powerful with current multi-wavelength
data, but that future radio surveys with eMERLIN, LOFAR etc. (and ultimately
the SKA) will greatly increase the power of the morphology and spectral index
methods. As an example of the science possible we derive the IR luminosity
density from the radio-selected SFGs using the radio/IR luminosity correlation.
We also examine the contribution by luminosity to the total IR luminosity
density and find evidence that fraction of LIRGs remains constant or decreases
above z=1 while the relative fraction of ULIRGs continues to increase up to
z=2.5.
