In 2005, Grayson was awarded the NZ Prime Minister's High Performance Scholarship.

[6] Throughout his junior career, Grayson won the U-13, U-15, U-17, U-19 New Zealand age group national titles.

A year later, in 2006, Grayson won the bronze medal at the 2006 World Doubles Championships in Melbourne, Australia, with his partner, Martin Knight.

[11] As part of the New Zealand High Performance Program, Grayson relocated to Halifax, West Yorkshire, England (2007 - 2009).

Previously, Grayson was based in Boston, as the touring squash professional at Cross Courts Academy, in Natick.

[19][20] Grayson participates in urban squash initiatives such as Harlem-based StreetSquash, which aims to improve the lives of inner-city children in Harlem through the game of squash; Grayson played for the Harvard Club of New York City at the 2015 StreetSquash Cup.