Got strange behaviour when seen on small screen or mobile.
http://3dimages.clickreturn.co.uk/On small screen if you scroll down the page the top of the header shows cart icon and menu toggle.
then there is a gap and you got bar with social icons and again menu toggle. The first menu toggle doesn't work.
See attached screenshot
Comments
It looks you have forced somehow to show logo in "sticky" version of header, and it is source of your issue. Theme by default shows only menu in sticky header when page is scrolled.
Remove your modification and you should be fine.
With kind regards.