I removed the 2 duplicate versions of the server validations but it still does nothing at all. The page is hidden on my website so if you want to see for yourself you can view it here:
it's almost like the submit button isn't a submit button at all, just a button with no behavior attached, but it definitely is a submit button - I have checked the code.
I have noticed it has this onclick code attached though - onclick="clearAllServerErrors('SiteDesignerOrderForm_YellowCircleThemes_YCSiteimportedcolours')", which to me looks like it just gets rid of errors if they were corrected. I didn't add this code in myself, form builder did so I'm assuming it's needed.