This is not so much a question but more of offering what I have created to others in the community. I have been using the Node-Red add-on in Venus OS v2.70~5-large-18 to control my openEVSE car charger via MQTT. It maximises the available power from the PV array to charge the car. When there isn't enough power it will use what is stored in my BYD batteries and when they're depleted it uses the mains. It is now stable enough that I have placed the json file and a brief explanation on GitHub (https://github.com/thepaulcooper/victron-openEVSE).
Disclaimer: I am not an expert in JavaScript or Node-Red so I am sure there are more effective ways of coding what I have created. But it works and I am now charging my car from the sun.