Hi Mark
Disclaimer: I am NOT an expert in anything except eating chocolate!!
1
I had a look and it seems the options do not show if they extend beyond the form, I am not sure whether you noticed this or not.
2
div#cck1r_top-b
Attached diagram "fields-visible.jpg" shows that if you make the form bigger by adding padding to div#cck1r_top-b then all can be seen.
3
div#form-validation-field-0
I reckon the answer is found with div#form-validation-field-0. It has the class open.
There is a script that looks like the culprit, could be wrong though...
http://pierceandco.co.uk/bt/templates/bt_property/js/bootstrap-select.min.js
PS
When I work out how to add an image to this forum, I will... pretty confusing so far, not sure how to do it.