Many apologies - I've discovered that the process above causes FAQs to be sorted by the order of entry (which for our sites happened to be alphabetical).
To sort alphabetically, you'll need to do the following:
1) Follow the above process, but instead of OrderBy.Text, use OrderByAlphabet.Text.
2) Modify the stored procedure FAQSearch, and add the following line at the end:
CASE WHEN @OrderBy=4 THEN CAST(f.Question as VarChar(8000)) END ASC
Remember to add a comma at the end of the preceding line, and you should be in business.