@KennethLavrsen @AaronCake Thank you both for that, I believe it was a combination of a few things, and as it comes up on the forum 50 times without a solution I’m going to try and explain it so when I forget 3 weeks later I can do it again… 
I had already established a connection which was confirmed via the MQTT mosquito broker log:
1598398605: New client connected from 192.168.0.34 as brainESP32 (p2, c1, k15, u'*****').
When I set up my switch as above I could confirm it was being published to the broker via configurations>intergrations>(MQTT)configure. when I typed a ‘#’ in the listen to a topic box and started listening I could see the message being published:
Message 15 received on office/light1/switch at 9:40:
ON
QoS: 0 - Retain: false
Based on @KennethLavrsen advise I had to include client.subscribe("office/light1/switch"); this was missed when following the mqtt_basic example. again thank you, I slotted this in the reconnect loop:
void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
Serial.println("Attempting MQTT connection...");
// Attempt to connect
if (client.connect(ID, HA_USER, HA_PASS)) {
Serial.println("connected");
//publish test connection
client.publish("outTopic", "hello world");
//subscribe to topics
client.subscribe("office/light1/switch");
}
else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
delay(5000);
}
}
Additionally, as I had changed my configuration.yaml so much to get it to work I was using the original "/office/light1/switch/" i used to subscribe likewise. Again @KennethLavrsen pointed out it should as per the outgoing message to the broker so after rechecking the configuration.YAML I had to update the Arduino code accordingly by removing the ’ / ’ on either end:
("office/light1/switch") vs ("/office/light1/switch/")
This resulted in the message passing successfully!!!:
10:20:25.075 -> Topic: office/light1/switch
So now we can read but the read is not executing as expected. therefor I added under Serial.println(topicStr) to check the payload message as per the comparison I was doing below:
Serial.print("payload: ");
Serial.println(payload[0]);
and when i ran it again received on the ardiuno serial monitor:
10:50:13.315 -> Topic: office/light1/switch
10:50:13.315 -> payload: 79
Still, it is not working but this is OK as I’m using a comparison of:
if (payload[0] == 'ON') /if (payload[0] == 'OFF')
and 79 is not ‘ON/OFF’ rather it is the first byte ‘O’ in ASCII. So some slight changes to look at the payload as a string will fix this:
payload[length] = '\0';
String payloadStr = String((char*)payload);
Then change if (payload[0] == 'ON') /if (payload[0] == 'OFF') to if (payloadStr == 'ON') /if (payloadStr == 'OFF')
So at this point, it works, BUT!!! The next step is to incorporate @AaronCake warning and removing the Publishing from the callback as per the PubSubClient and instead set a flag. sure it works, but this could lead to issues later on, so better safe than sorry
This leaves me with:
#include <ArduinoJson.h>
#include <WiFi.h>
#include <PubSubClient.h>
#include <WiFiManager.h>
unsigned long updateCurrentMillis;
unsigned long lastUpdateDelay;
unsigned long updateDelay = 1000;
// MQTT Network
const char* mqtt_server = "192.168.0.200";
//Node ID
const char *ID = "brainESP32"; // Name of our device, must be unique
//Topics
const char *TOPIC = "room/light"; // Topic to subcribe to
const char *STATE_TOPIC = "room/light/state"; // Topic to publish the light state to
int officeLight1Status;
// Home Assistant Credentials
const char *HA_USER = "****";
const char *HA_PASS = "****";
WiFiClient espClient;
PubSubClient client(espClient);
void callback(char* topic, byte* payload, unsigned int length) {
String topicStr = topic;
String payloadStr = String(( char *) payload);
Serial.print("Topic: ");
Serial.println(topicStr);
payload[length] = '\0';
String s = String((char*)payload);
Serial.println(s);
if (topicStr == "office/light1/switch") {
//turn the switch on if the payload is '1' and publish to the MQTT server a confirmation message
if (s == "ON") {
Serial.println("light on");
officeLight1Status = 1;
}
//turn the switch off if the payload is '0' and publish to the MQTT server a confirmation message
else if (s == "OFF") {
Serial.println("light off");
officeLight1Status = 0;
}
}
}
// Reconnect to client
void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
Serial.println("Attempting MQTT connection...");
// Attempt to connect
if (client.connect(ID, HA_USER, HA_PASS)) {
Serial.println("connected");
//publish test connection
client.publish("outTopic", "hello world");
//subscribe to topics
client.subscribe("office/light1/switch");
}
else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
delay(5000);
}
}
}
void setup() {
// put your setup code here, to run once:
Serial.begin(115200);
client.setServer(mqtt_server, 1883);
client.setCallback(callback);
setup_wifi(); // Connect to network
delay(1500);
}
void setup_wifi() {
Serial.print("\nConnecting to ");
//WiFiManager
WiFiManager wifiManager;
Serial.println("started");
//wifiManager.resetSettings(); // turn off after intital settings are done ****** turn on if needing to resetup wifi
wifiManager.setCustomHeadElement("<style>html{filter: invert(40%); -webkit-filter: invert(40%);}</style>");
WiFiManagerParameter custom_text("<p>This is just a text paragraph</p>");
wifiManager.addParameter(&custom_text);
wifiManager.setAPStaticIPConfig(IPAddress(100, 100, 100, 100), IPAddress(100, 100, 100, 100), IPAddress(255, 255, 255, 0));
wifiManager.autoConnect();
while (WiFi.status() != WL_CONNECTED) { // Wait for connection
delay(500);
Serial.print(".");
}
Serial.println();
Serial.println("WiFi connected");
Serial.print("IP address: ");
Serial.println(WiFi.localIP());
}
void loop() {
if (!client.connected()) {
reconnect();
}
client.loop();
delay(100);
if (officeLight1Status != 3) {
if (officeLight1Status == 1) {
client.publish("office/light1/status", "ON");
}
else client.publish("office/light1/status", "OFF");
officeLight1Status = 3;
}
updateCurrentMillis = millis(); //send update every x seconds
if (updateCurrentMillis - lastUpdateDelay >= updateDelay) {
lastUpdateDelay = updateCurrentMillis;
switchOut(); //dump data
}
}
void switchOut() {
const size_t capacity = JSON_OBJECT_SIZE(26);
DynamicJsonDocument doc1(capacity);
DynamicJsonDocument doc2(capacity);
doc1["pbrAM"] = 0;
doc1["pbrSS"] = 0;
doc1["lightAM"] = 0;
doc1["lp_1"] = 0;
doc1["lp1_1"] = 0;
doc1["lp1_2"] = 0;
doc1["lp1_3"] = 1;
doc1["lp1_4"] = 0;
doc1["lp_2"] = 0;
doc1["lp2_1"] = 1;
doc1["lp2_2"] = 0;
doc1["lp2_3"] = 0;
doc1["lp2_4"] = 0;
char buffer[256];
size_t n = serializeJson(doc1, buffer);
client.publish("brainOut1", buffer, n);
doc2["tempAM"] = 0;
doc2["tempSS"] = 1;
doc2["airAM"] = 0;
doc2["airSS"] = 0;
doc2["doseAM"] = 0;
doc2["doseSS"] = 1;
doc2["dosephU"] = 0;
doc2["dosepHD"] = 0;
doc2["doseNut"] = 0;
doc2["doseSam"] = 0;
doc2["doseFill"] = 0;
doc2["harvsetAM"] = 0;
doc2["harvestSS"] = 0;
n = serializeJson(doc2, buffer);
client.publish("brainOut2", buffer, n);
}
Again thank you for the help guys!