The biggest mistake I made was I "Assumed" which is one of the worst crimes IMO.
I assumed that this: https://shop.pimoroni.com/products/phat-stack?variant=658973392906 was a bit like an extension of the GPIO pins on the raspberry Pi (The Pi is fine and works normally) The screen did work when connected directly to the Pi via the GPIO pins. There is like a white halo light around the screen indicating power and when the Pi boots then the screen displays the boot sequence (This is important I will mention it again) I then shutdown, disconnected the screen and connected it to the last section of the pHat Stack (with the screen facing away from the stack so the stack would be on the left and most of the screen on the right (I have no idea what orientation the screen should be attached to the GPIO pins)) I then attached the GPIO cable to the Pi and powered on.
1. There was no Halo light and no screen output.
2. I then discovered I had the GPIO cable connected the wrong way round and not laying across the Pi as per instructions.

I disconnected everything, connected the screen directly to the Pi and again, no white Halo, no screen output. I figure I've blown something by running power through the wrong connection or something.

Bit annoyed at myself tbh, I've stumped up another £32 for a replacement.