Well not CSS at all - I forgot that OPC uses template_default a lot.
Removed most of tpl_modules_order_totals.php from there - fixed my issue !
But thanks for your interest - may I explain that I retired long long ago just as CSS was starting to appear so never really bothered with it.
I may be the only guy left whose first experience of a program crash meant I had dropped the tray holding the punched cards !