Hi and thanks for the replies
As I said in the original post, I am confident it was wired correctly, as keypad was illuminated, power light was on, together with the Unset and Tamper indicators. I am also sure the data connections were correctly wired as after initial power up, I was able to enter the default user code and default engineer code to silence the panel warning bleeps via the keypad.
I do believe the keypad is faulty, as I removed the PCB from the plastic housing and the display came to life, however, when I replaced it back into the housing, the display went off again. After repeating this two or three times, I have now managed to get the display on permanently, but I am not happy that it is likely that it could fail on me again at any time.
Once again, thanks for your replies and confirming I wasn't doing anything wrong.