Hi mate,
I only joined today, but may be able to help. Part of my job some time back, was controlling the aged debtors for a large company.
From what I've read, you are due the whole amount - case closed.
Use this format in future and don't make idle threats, do what you say you are going to do, or they will very quickly see you as a soft touch.
Once an invoice is due...
1. Send a reminder asking for payment within 7 days.
2. No payment in 7 days! - request payment by return, or legal action will commence with no further contact.
3. No payment by return! - Instruct your solicitor to send a 3 day letter.
4. No payment in 3 days! - Instruct your solicitor to commence county court action, to include ALL legal costs and interest on the debt.
If they have no case, they will generally pay upon reciept of the court papers, as they will not want a ccj against them.
They sometimes try to just pay the amount owed and not the costs, don't accept. Why? because they were warned and decided to ignore it!!
If they don't reply to the court papers, you will have judgement and the solicitor will advise on how to enforce the judgement.
Also, if they request a payment schedule, ie; so much per month, refuse the request on an amount this small.
Any other advice, please ask...