Got it working in the end, here is the code if anyone else has the same problem;
alias: Vehicle Entering the Driveway
description: ''
trigger:
- platform: mqtt
topic: BlueIris/In/Status
condition:
- condition: template
value_template: '{{ trigger.payload_json.trigger == "ON" }}'
action:
- service: notify.mobile_app_iphone
data_template:
title: Driveway Activity
message: 'Vehicle - {{ trigger.payload_json.plate }} - has entered the drive'
mode: single
rgds,
Marcus