i would like the slideshow to have the width as the navigation menu and respond to different devices as the navigation width would.
Heres a link to the website in question http://test.amplifyevents.uk
Just change the width of rev_slider_1_1_wrapper
to 100%? Your slider will be lining up with Home, not with the complete left of the nav-bar, but that can probably be fixed with a margin.
#rev_slider_1_1_wrapper { width: 100% }