Thank you for your help and assistance in following through this job application. I'm sorry that I didn't come up to the mark on the support application they had open. They would have been a good employer and I felt that I could have had success in that company.
I would be pleased if you kept my details on file as I am determined to get a position in the next 3-4 months if possible. It was nice to feel that you actually cared as a company what happens to your clients, a rare commodity these days.

Thanks again, and please call if there are any other vacancies.

Warm regards,

David