JT007:
Im not able to find a way of breaking into the code on the master to allow PC interface/interaction, i want to be able to send and receive serial data from the master.
I don't know what you mean by "breaking into the code". If you want to have device-to-device and also communicate with a PC you probably need two serial connections (eg. software serial and hardware serial).
I have added a second serial connection in the code with a 9600 baud rate and it works at sending and receiving from the master whilst its running the 485 link however i don’t quite understand how to write or read data to be used in the 485 message.
I don't understand that question, if it is a question.
The second question is how to understand the slaves return message, are you able to provide an explanation as to how this is achieved.
as far as i can figure out there is a return response which the master hears and hold LED on pin13 low unless there is a broken link, corrupted message or i guess a time out.
As far as the RS485 stuff goes, with only 2 wires you can only have one master. So the master has to send a message "addressed" to one slave and stop being a master. Then the addressed slave becomes a master and replies. Then the master resumes being a master again. You would need some sort of time-out in case the slave doesn't reply.