No, he was not based on a real person.

Rowling states this categorically in a 2004 interview

Are any of your characters based on real people?

The only character who is deliberately based on a real person is Gilderoy Lockhart. [...] Other people have contributed the odd characteristic, such as a nose, to a character, but the only character who I sat down and thought that I would base on someone is Gilderoy Lockhart. It made up for having to endure him for two solid years.

He claims the same in the old J. K. Rowling website (probably written in 2005 or 2006):

I have only once set out to depict somebody I have met and, unlikely though it might seem, the result was Gilderoy Lockhart.

See also Who is Gilderoy Lockhart based on?

No, he was not based on a real person.

Rowling states this categorically in a 2004 interview

Are any of your characters based on real people?

The only character who is deliberately based on a real person is Gilderoy Lockhart. [...] Other people have contributed the odd characteristic, such as a nose, to a character, but the only character who I sat down and thought that I would base on someone is Gilderoy Lockhart. It made up for having to endure him for two solid years.

He claims the same in the old J. K. Rowling website (probably written in 2005 or 2006):

I have only once set out to depict somebody I have met and, unlikely though it might seem, the result was Gilderoy Lockhart.

See also Who is Gilderoy Lockhart based on?

No, he was not based on a real person.

Rowling states this categorically in a 2004 interview

Are any of your characters based on real people?

The only character who is deliberately based on a real person is Gilderoy Lockhart. [...] Other people have contributed the odd characteristic, such as a nose, to a character, but the only character who I sat down and thought that I would base on someone is Gilderoy Lockhart. It made up for having to endure him for two solid years.

See also Who is Gilderoy Lockhart based on?

No, he was not based on a real person.

Rowling states this categorically in a 2004 interview

Are any of your characters based on real people?

The only character who is deliberately based on a real person is Gilderoy Lockhart. [...] Other people have contributed the odd characteristic, such as a nose, to a character, but the only character who I sat down and thought that I would base on someone is Gilderoy Lockhart. It made up for having to endure him for two solid years.

He claims the same in the old J. K. Rowling website (probably written in 2005 or 2006):

I have only once set out to depict somebody I have met and, unlikely though it might seem, the result was Gilderoy Lockhart.

See also Who is Gilderoy Lockhart based on?