Custom CSS manipulation for donate_button on Fundraising Plugin

Dear Support,

I am struggling to centre align a "donate_button" shortcode. All attempts leave it left aligned. Whether I try through the Custom CSS in the Fundraising settings or whether I try and centre within the text box the shortcode is sitting in.

I have also tried different styling (basic, minimal, etc) but to no avail.

I am focusing my attention on form.wdf-basic/form.wdf-minimal in the Custom CSS. Perhaps I am looking/trying in the wrong place?

I have attached an image for clarity. The site is currently in development at http://e01b49.com/hedal44org/ the donate buttons are on the home page.

Thanks in advance to anyone out there who can point me in the right direction.

All good wishes,
Will