Ok, changed the attribute from "Read Only" to "Radio" and got around the undesired *Please Choose:* by changing includes/languages/english/product_info.php

from this
define('TEXT_PRODUCT_OPTIONS', 'Please Choose: ');
to this
//define('TEXT_PRODUCT_OPTIONS', 'Please Choose: ');
define('TEXT_PRODUCT_OPTIONS', 'Please Note: ');
and saved the file using the override system.

So I guess the attribute could now be used to control the display of this bit of code:

<!--bof practitioner details-->
<fieldset class="shipping" id="comments">
<legend><?php echo TABLE_HEADING_COMMENTS; ?></legend>
<?php echo zen_draw_textarea_field('comments', '45', '3'); ?>
</fieldset>
<!--eof practitioner details-->
Again, the box should only appear if the cart contains no products with products_options_id = 2

Any hints please?