Hi Stewart,
I'm no expert on this - I find VM wild and wacky pricing layout as stupid and mis-labelled as the next man...
All I can say is our template displays exactly as per the std VM template (afaik) - we just copy and pasted the code
you can test this with Puremart completely disabled.
To do this just rename the folder
ROOT/templates/YOUR_TEMPLATE/html/com_virtuemart
to
ROOT/templates/YOUR_TEMPLATE/html/com_virtuemart2
if your using over-rides set them off as well in Configuration->Templates
You can see the code in the templates/your_template/html/com_virtuemart/productdetails/default.php ~ line 442
I solved one today here -
www.flexiblewebdesign.com/index.php?option=com_kunena&view=topic&catid=18&id=886&Itemid=234
scroll to the bottom (she hasn't thanked me yet)
Just play around ticking and un-ticking as I would .. you'll get there...