Began playing at the age of ten at Mountain Ash GC in South Wales with his dad, David. Was a talented footballer and had trials at 16 with Manchester United, Crystal Palace and Luton, but chose a career in golf, starting a four-year scholarship at West Florida University in 1998. Part of the winning Walker Cup side in 2003.

Won his first European Challenge Tour title at the 2013 Finnish Challenge, and he has qualified for the European Tour through Qualifying School on six occasions.

Represented Wales in the 2014 World Cup of Golf, where in his final round he had one of the most bizarre level par 72s ever recorded. After starting with two birdies at Royal Melbourne, he had a hole-in-one on the short third before carding an 11 on the following hole en route to finishing tied eighth.

Five years after becoming a Challenge Tour winner for the first time, Manley secured his second title at the 2018 Hauts de France Open, defeating Grant Forrest on the third extra hole. That helped secure a return to the European Tour as he finished ninth in the Rankings to graduate from the second tier.

Won his third Challenge Tour title at the Euram Bank Open in 2021.