customer not paying over due invices

I have a customer who is overdue by 49 days over the 30 day credit on one invoice and 22 days over on another invoice.

I have logged all the calls and emails I have made trying to get the payment out of the company.

I am now being fobbed off as the financial assistant will not take my calls or answer my emails.
The financial director always seems to be out of the office or in board meetings.

They owe £10,080.00 over the two invoices and I have done everything I can to get these invoices paid.

In my last email I advised them I would charge them late payment interest and other charges if they did not pay the invoices within 7 days. no response.

Where do I go now? any advice would be greatly appreciated

Hi David
the credit terms are 30 days and agreed to by the financial director. There is no dispute on either invoice.

I have sent a registered letter before action with interest & compensation as per late payment on commercial debt act 1998 today. I used your calculator to work out the interest.

I have also explained that we have full ownership of the material pertaining to these invoices since the invoices are not paid for and revoke their right to use the material.
So if they want to use the material hopefully they will pay

They have been fobbing us off with all sorts of excuses and I have now given up trying to appeal to their better nature

Thanks for the advice and I will keep you updated