With almost certaintiy, it would appear that William Townley, the first person to score a hat trick in the FA Cup and third cousin of my great grandfather, is indeed Billy Townley, who played for the Blackburn Rovers and later was a pioneering coach for teams in Europe.
I was able to obtain the birth certificate that shows a birth date of 14-Feb 1866, which conforms with the short bios I have found on the internet.
Birth Cert details below:
Who: William Townley
Birth Date: 14- February 1866
Where: 64 Lark Hill Terrace, Blackburn, Lancashire
Father: Dan Townley, Iron Turner
Mother: Elizabeth Townley, formerly Holden
Registered: 24-March 1866
Registrar: William Barlow Fairbrother
Source: 1866 Vol. 8e , Page 331
See:
http://en.wikipedia.org/wiki/William_Townley