Get the paperwork in order stating that deposits are non-refundable, payment before pulling the trigger etc. Get it signed sealed before the day leaving you with every power to get your money whether they turn up or not. I help afriend run a corporate event business, our contract has them paying pretty much every penny from the moment they sign their name, even if they cancel.
With these two jokers, naming them is your right, if they pay you you can make a statement to that effect and thank them very much. The fact they payed late will still be of infomrmation to others. I would personally give them a letter stating you want the balance within 5 working days or else you will start claims in the small claims court. (cost you nowt to do it, and I never lost a case yet). Also state in the letter that you will be charging interest of 5%/per week outstanding. If you go to court make the papers out and include losses etc, you will be able to claim 3-4 times their bill. If I can help please contact me on james.mason68@btinternet.com I'm happy to aid with getting your money. I'm disabled so I've got the time to do it.
James