Checkout won't proceed to payment

I'm using OpenCart Version 1.5.1.3
I have virtually finished creating a custom theme for my website, one last hurdle I am trying to overcome is the checkout process.

I have enabled all of the suitable payment and delivery options in the admin section of the site, yet when I go to process a dummy transaction, I cannot progress from Stage 4: Delivery Method to Stage 5: Payment Method. I am using a custom theme, but haven't altered anything that would effect the payment process (that I can think of).

Any ideas anyone?


Thanks in advance!

So after trying a few things, its down to the fact that I've changed the template. If I swap it back to the default template, it works fine. Next question....which file(s) have I broken? Any ideas?