Theme Broken after Upgrade to 3.2.8

My site at https://www.gap.works is broken in Internet Explorer 9.

The site renders in a columnar format, all squashed towards the centre with widgets from the right side placed below the content, etc. The footer doesn’t render its background, etc.

It looks like its trying to render the responsive mobile theme, but on a PC install of IE.

A little bit urgent as the site is live and has a marketing programme attached and running!

Here’s a cludged together screenshot.

It renders very nicely on Chrome, Firefox and not too bad on Android mobile, although Chrome does some clipping of the slider heights, and hides the action buttons!