Sorry to hear this is causing you so much stress!
I don't really have any tips for this scenario.. but wonder if the business practises of one of my suppliers might help for the future?
They offer "discounts" if invoices are paid within the set period.
I'm sure this is built into the price though - so essentially acts as a surcharge for late payment.
They then contact you with a friendly reminder the week before the invoice is due to remind you of the "saving" - it gives them a good excuse to put their foot in the door and make contact with their "good guy face" on as they are saving you money.
