Ja dalem cos takiego:
Please accept this as formal notice of my resignation from the position of <POSITION>, with effect from <DATA>.
In accordance with my contract of employment I am happy to continue to work until <DATA Z WYPOWIEDZENIEM>.
Could you please confirm to me any holiday entitlement that has not yet been taken, and whether you are willing to reduce my notice period to take this into account, or perhaps buy out this entitlement, retaining me until notice has been fully worked.
I have decided that it is time to move on and I have accepted a position elsewhere. This was not an easy decision and took a lot of consideration. However, I am confident that my new role will help me to move towards some of the goals I have for my career.
I wish both you and <FIRMA> every good fortune and I would like to thank you for having me as part of your team.
In my departure, I trust I may use your name as a referee for future employers, and I again thank you for the experience I have gained.
If I can be of any help during this transition, please let me know.
<IMIE I NAZWISKO>