Page seem to have a column

So, I have inserted the booking form via shortcode and then underneath and tried to insert a horizontal line. Within the shortcode it allows me to specify width. Firstly this was set to 800px and then the line would appear for about an inch at the top right hand side, so next to the booking boxes.

I set the width to 100% and the line doesn’t now appear. You can see it flash up as the page loads then go away. I just want a line to appear above the text (Still not sure? Get a non obligation free quote in 30 seconds!)

When the shortcode said 800px I tried <p></p> and <br> but this just moved the line down while it was still on the right hand side of the booking box.

I don’t know what to do next. Any ideas? Can I insist that the shortcode element fills 100% of the width of the container?

The page I need help with: [log in to see the link]