Ring Wallcrete for a local installer.
Lord and Downing Ltd in Rotherham is Wallcrete approved.
There is a more less tradesman way.
You base coat and scratch as normal. Chalk out your joint pattern and apply 6mm thick mortar over the chalk lines then with a 10-13mm lath you cut your raised joints. Then once set,you mix some sharp sand, bit of lime, cement with cement dye mixed uneven and apply thick in the middle tapering out to just below the joint surface. Using the edge of a gauging trowel texture the mortar surface to expose the aggregate.
Was taught this at College in 72 and thought it was a waste of time. But have done it several times over the years.
There is an even faster way, taught me on Rhodes Island Greece. But you will need a wide variety of old saw blades. Thats going to take too long to explain but is fast and simple.