Although I haven't specifically done a study on individuals with the surname Willes it is however definitely a derivative of the Wills surname.
I did a study on the Wills surname and it's derivatives for over 15 years but found the task too big to follow every possible name linked. It is another area altogether as far as genealogy goes.
I have concentrated specifically on the Wills surname from the 1300s period where my tree commenced. With indexes of one kind or another I have seen many hundreds during the 1400s - 1700s with the Willes surname.These records are held at the Exeter Records Department in Devon, England.
It depends on the individual on how far you stretch your research.The Wills surname is now more than 900 years old and first found on record at Saltash in Cornwall England.
See my webpage on ORIGIN AND HISTORY OF THE WILLS SURNAME as there are many other names linked to the Wills surname.
Regards from Ian Wills.