[Therion] Controlling map location on page

I'm just starting with Therion. I have the same problem as a user back in 2012: http://comments.gmane.org/gmane.comp.gis.therion/3066 When using "export map" my map is at the top right corner of the page, with much white space to left and bottom. I could not see a satisfactory resolution in the above thread, although I assume its possible (simple). In the .th file I have defined: cs OSGB:SN fix 1.0 xxxx yyyy zzzz and in a "layout definition" in the .th file I have tried some combinations along the lines of cs OSGB:SN origin xxxx yyyy zzzz metres (or grid-origin...) but without any success in moving the map in the output pdf Thanks for any pointers...