Hborre, couple of things....

I guess I had to save the settings as a preset,  then hit the "apply" button because just closing the screen didn't save the settings, as it bounced back to default settings when I re-opened the script window. 

I also for some reason don't have the "pro output" options at the bottom as shown in your settings, here's a screengrab of mine.

I did an area render, and I had zoomed in with the main camera more on the face so it would be bigger and easier to see, but as soon as it began to render it automatically zoomed back out smaller to where I originally had the camera.

Kinda hard to tell with this small render. Let me know if I've got to change anything and I'll try a larger area tomorrow morning.

EDIT: Oops, just noticed I didn't have the "use own process" box checked. Ok, now the settings don't change when I load the preset I saved, something strange going on here. Will have to set it up and try it again manually in the AM.

Thanks for all your help, much appreciated

MM