Just though I'd share this with you. 'OpticVerve'. I've been using their PS filter plug-in (Virtual photographer) for a while and had no problems. They now have a stand-alone version of their own editing suite called 'Virtual Studio' which appears to have most of the editing tools you need for free. The list of tools is quite expansive, layers, curves, histograms and most of the other functions found in the pay-for software available elsewhere.
Link to the site
OpticVerve
Apologies if it's already been done. Did search