Homebridge MQTT plugin and Home Assistant

I have a separate MQTT broker running (Mosquito) and also have a separate instance of HomeBridge. I came across an excellent MQTT plugin for HomeBridge (https://www.npmjs.com/package/homebridge-mqtt) and have it working well with Node-Red and HomeKit. I’m waiting to also integrate it into Home Assistant (non HASSIO) but I’ve having issues.

I’ve set the topic in the MQTT plugin to be the same as the discovery prefix in Home Assistant and added a simple MQTT switch in the configuration.yaml but can’t get the two to talk to each other.

switch:
- platform: mqtt  
    name: "Siren"  
    state_topic: "homeassistant/to/set"
    command_topic: "homeassistant/to/set/Siren"
    payload_on: "ON"
    payload_off: "OFF"
    optimistic: false
    qos: 0
    retain: true

I’ve noticed the json format for Home Assistant and the plugin are different, is this whats causing the issues?

Any help grateful.