Changing Foreign Key from numeric to text. Now search does not work

Hi,

I created an admin section some time ago using the data assist wizard and it works very well. Now my client requires (for reasons involving a third party) that a foreign key used, is changed from a numeric ID (INT), to a text field (VarChar). I've done this and the basic insert, update and display works fine but the search does not. I have the search form on the results page as well as the normal separate file (I've attached them both). This particular search field (Region) is using a dynamic drop down menu.

The field involved is FKeventsRegionID. It used to be 1, 2, 3 etc but is now "England: South East", "England: East" etc

There is obviously something I've missed here but for the life of me it escapes me. Can you help please?

If you go here you will see a search on the right using a drop down. This works fine. This site is still using the old code but on my testing server it works fine.

Any help appreciated.