Customise My Search Not Acting As Expected

Hi,
I am having problems with Advanced Search “Customise My Search”.
My site is http://schoolbizmap.com/ and is based on Schools. I am trying to set things up so that schools can add a “Business Offer” from a list of possibilities, and then users can search to find all schools that have that “Business Offer”.

This is what I have set up:
In Place Settings I have a form field called Business Offer where I have 6 Option Values
Curriculum, INSET, Secondments, School Direct, Equipment Hire, Clubs.
I have ticked the box “select if you want to show option in filter”.

To check how this works I have created a Place “Mobile School Websites – Creators of SchoolBizMap” and added all these 6 Option Values. They show in the tab “Business Offer” shown here:
http://schoolbizmap.com/places/united-kingdom/bristol/other-1/mobile-school-websites/

When I go to the full map http://schoolbizmap.com/full-page-map/ and do a Customised Search and tick a box in the dropdown, the result is “No listings found which match your selection.”

Am I misunderstanding what the customised search can do, or have I set things up incorrectly?

Thanks for any advice you can give.
Ian