Hi Alun,
That looks good. You can now see emission lines of H-alpha, H-beta and H-gamma plus the two [N II] lines bracketing H-alpha and the dip at 5896 due to Na absorption in our galaxy. You could get three independent estimates of the redshift from the three Balmer lines. I’m guessing you haven’t applied a correction for instrument and atmospheric losses? If you did this it would remove the hump and you’d end up with a relatively flat spectrum similar to this one on NED http://ned.ipac.caltech.edu/spc1/2006/2006ApJS..164…81M/NGC_2903_nuc:S:Opt:mk2006_sp.png
Cheers,
David