"I am genuinely grateful for your help and the outstanding result in the circumstances"
I just wanted to write to you personally to thank you for your assistance and help over the past few months.
Your reassurance and professionalism helped me enormously in a difficult time. I am genuinely grateful for your help and an outstanding result in my circumstances.
I would be happy to act as a reference for you at any point in the future.
All the very best for the future.