The default is one PCB circuit design per panel, though if you provide the complete panel design - you can have as many as you wish, as long as they fit of course.

If you want multiple  PCB designs on one panel, where www.PCBpanel.co.uk do the design layout - this service is offered too.  You simply need to select the 'multiple by us' option in 'Number of PCB designs on the panel' when placing your order.  When you send the relevant Gerber files, we'll need some notes on how you want then designs laid out.