I have only ever had 2 non payers in 14 yrs of running my business. And both have involved the company owing me money going into receivership, to have as many as you have had in just a few short months I have to ask myself are you up to the Job? As your customers must obviously think you are not. In my experience a happy customer always pays. There are 2 sides to every story what are your customers saying as to why they are withholding payments?