Z-Index issues with my drop-down menu

Hi

Can anyone help please, in advising how I go about ensuring that the jQuery drop-down menu widget is uppermost on the page. It seems to be suffering z-index issues when faced with the image slider on the home page – https://www.ukmartin.com and with the Twitter widget on one of the team pages – e.g. https://www.ukmartin.com/chris-harris/

Assistance would be much appreciated.

Thanks

Martin