Finally resolved this for any future readers.
To fix this ensure you are using the WPGraphQL Plugin available directly from searching in the WordPress Plugin Directory. Link for reference: https://en-gb.wordpress.org/plugins/wpgraphql-acf/
Then in your Custom Post Type settings within the ACF area, toggle the Advanced settings and with the above plugin installed you should now see a new GraphQl area. Toggle the Show in GraphQL option and you should be good to go.
It seems the WPGraphQL ACF plugin available on the WPGraphQL Website is out of date and should really be updated to link to the newer version.
