Dear Mr. Clark,
The reason for writing this letter is that I feel sorry to inform you about my absence in the coming months at your retirement housing in London. This was such an honour to support and comfort the elderly by exchanging interesting stories with them for the last two years. Thereby, I have found joy not only by looking at their smiley faces, but also they have provided me valuable experience in return.
My company is going to establish a new branch next month in Bath, which is pretty far away from London. In the meantime, my top manager recommended me act as branch manager there since he has confidence in my abilities and management skills. Honestly, that offer was such a great opportunity for my future career and promotion prospect, thus, I could not refuse it.
Although I would not continue my voluntary work in the near future, I would like to introduce one of my close colleagues named Michelle, who is absolutely compassionate with helping the others in her spare time. I shared with her about the regular tasks in your organisation and she was really interested in it. Please find her contact in the attached file and she would be happy to meet you personally.
Yours sincerely,
Hiep Do