So, I have had some good results with online mastering sites - I have used eMastered. Their free trial has come to an end and they are now operating a subscription model, or pay per track. Is there a software plugin that does the equivalent which I could buy for a one off fee?
 
Sure, I know that there are lots of options out there with lots of knobs to twiddle, but with eMastered and I suspect many other online mastering services there are no controls - just upload and let the software do its "magic". I know these are not the be all and end all, but I often get good results. 
 
Bill

You could try http://www.curioza.com/#aams
 

With IK's Lurrsen or O7A, you can just "flip through the presets" till you
find something you like.  Lurssen is obviously the cheaper ( and has the 
least amount of "fiddling" capability) of the two...

Or take a look at this excellent software.
http://www.magix.com/us/audio-cleaning-lab/audio-music-lab-premium/
It has some ready-to-go mastering presets, or yo can tweak any parameter. 32-bit only, though.

Ooops...forgot to mention one of the easiest...

Softube Drawmer S73

http://www.softube.com/index.php?id=drawmers73
 
Still has knobs...but very minimal and easy to use and sounds good...

There is also....http://www.har-bal.com/
 

cclarry
Ooops...forgot to mention one of the easiest...

Softube Drawmer S73

http://www.softube.com/index.php?id=drawmers73
 
Still has knobs...but very minimal and easy to use and sounds good...

Didn't appreciate there was so much choice - Drawmer looks and sounds especially interesting. 
 
Thanks for suggestions so far