  (Abridged) Narrow Line Seyfert 1 (NLS1) galaxies have low mass black holes
and mass accretion rates close to (or exceeding) Eddington, so a standard
blackbody accretion disc should peak in the EUV. However, the lack of true
absorption opacity in the disc means that the emission is better approximated
by a colour temperature corrected blackbody, and this colour temperature
correction is large enough ($\sim 2.4$) that the bare disc emission from a zero
spin black hole can extend into the soft X-ray bandpass. Part of the soft X-ray
excess seen in these objects must be intrinsic emission from the disc unless
the vertical structure is very different to that predicted.
  However, the soft excess is much broader than predicted by a bare disc
spectrum, indicating some Compton upscattering by cool, optically thick
material. We associate this with the disc itself, so it must ultimately be
powered by mass accretion. We build an energetically self consistent model
assuming that the emission thermalises at large radii, but that at smaller
radii the gravitational energy is split between powering optically thick
Comptonised disc emission (forming the soft X-ray excess) and an optically thin
corona above the disc (forming the tail to higher energies). We show examples
of this model fit to the extreme NLS1 REJ1034+396, and to the much lower
Eddington fraction Broad Line Seyfert 1 PG1048+231. We use these to guide our
fits and interpretations of three template spectra made from co-adding multiple
sources to track out a sequence of AGN spectra as a function of $L/L_{Edd}$.
  The new model is publically available within the {\sc xspec} spectral fitting
package.
