I need marketing letters to be written

Kind of letter: Business
Num. of words: 300
Topic: Accounting and Tax services
Tone: Sincere
Outline & Structure: We are a firm of accountants and one of our client who runs a security guard company has a number of workers as self employed or as limited company.

I want 3 letter approach as follows;

1st letter from my client who is already providing them with work sincerely praising the quality of work that we produce and they are happy as we provide them with very personal one to one service.

2nd letter from us telling them that you were approached by so and so. We provide tax and accounting services blah blah blah. We can offer you our services for a fixed price of £450+VAT 3 years guarantee not to increase your fee and If you pay by standing order we can offer a further 20% discount in the joining year.

3rd letter is follow up to 2nd letter.

Lastly, A brochure leaflet letter(A5) to go with the greeting cards for Christmas and New Year.
Extra notes: These letter should be written in a way so we can send them via post as well as by e-mail.