Invoice as a method of payment

HI, I noticed that the business sellers can choose between ‘standard’ and ‘invoice’ payment method. I am a small seller so standard method is ok for me - after confirming the dispatch money goes to my account - but I just had a customer with invoice payment and in this case I guess I have to dispatch the item with the invoice and patiently wait for the payment… Does anyone has any experience with business sellers NOT paying the invoices? What do you do in this case? I sell dvd’s so checking if the payment arrived and chasing someone for a couple of pounds it’s not really what I want to do… The other thing is I always thought that Amazon should look after the payments so the usual seller shouldn’t worry about it as the buyer pays at the moment of the transaction but it is not true! Invoice payment is not an immediate payment and if you confirm it the money is not in your account… - so you should deal with the buyer after that:) Thanks for any advice - as I said my dvd was only a couple of pounds but what to do if the item is expensive and not paid??