Cresswell, who joined Adding Value in 2006 as part of the founding team, said she is looking to "pursue personal aspirations".
She said: "I feel I can look back on the past eight years with huge pride. I’ve enjoyed my time at Adding Value immensely and have built some really great relationships. I will leave on the best possible terms and wish Tina, Randle and all the team the very best for the future."
Randle Stonier, founder and CEO of Adding Value, added: "Charlotte has made a huge contribution to Adding Value and our growth during her time with us. She will be sorely missed and we wish her every success in this next exciting chapter of her life."