Not to worry. Figured it out. For anyone else you could try this... Edit the html as follows:
..
..
<body>
<div style="position: absolute; left: 50%;">
<div style="position: relative; left: -50%; border: 1px solid rgba(238,238,238, 0.8);">
..
put the rest of the SSUB generated BODY code in here
..
</div>
</div>
</body>
Note I added the "border: 1px solid rgba(238,238,238, 0.8);" just to see the outline of my interface. You can remove that bit. Hope it helps someone.