I can’t help any further without a live URL to view.
You can access the URL now: https://bdsdrivingschool.co.uk/reviews/
Your theme is using the select2 library. In the functions.min.js file of your theme it runs the following code:
Unfortunately, this code does not provide a way to exclude dropdowns from being transformed by Select2.
You might want to contact the Theme developers and request that they change that line to this:
Until they make that change, the only way to fix this is with a code snippet: https://pastebin.com/yXCUmqX2