Name,
Position,
Organisation
Name and Address
Date
Dear (line manager name)
Please accept this as formal notice of my resignation from the position of (your job title and site/department/division as applicable), with effect from (normally date of the letter or receipt of letter - check your contract - if in doubt refer to date of letter).
While I believe that I am moving for good reasons, I am sorry to leave, and I thank you for your support during my time with the company, which I have found enjoyable and fulfilling.
Please let me know the arrangements for handing back (equipment, company car, etc,) and handing over outstanding work and responsibilities.
Yours sincerely (your name)