Brett’s Five Hymn Voluntaries has recently been published by Wirripang. It includes Voluntaries on Tallis’ Canon, Wachet Auf, Wilhelmus, St Oswald, and Repton. It can be purchased as an instant download or sheet music here: https://www.australiancomposers.com.au/products/five-hymn-voluntaries?_pos=49&_sid=a555960c9&_ss=r.

You can also hear a performance of the Voluntary on Repton by James Flores here: