Ray - On each of the Add to Cart pages, I had set the Quantity to 1 and Action as Ignore (there doesn't appear to be a 'hidden' option. On the Cart page - I have changed the state of the Quantity server behaviour to 'read-only' - will that work?
This is how the code reads now:
<input name="Progs_Quantity_<?php echo $Progs->DisplayInfo("WAUID"); ?>" type="text" id="Progs_Quantity_<?php echo $Progs->DisplayInfo("WAUID"); ?>" onkeypress="waec_showUpdate('Progs_Update_Quantity_<?php echo $Progs->DisplayInfo("WAUID"); ?>',this);" value="<?php echo $Progs->DisplayInfo("Quantity"); ?>" size="3" readonly="readonly" />