Have plugged a "short" Ethernet cable into the disk that you are using to see if you are getting a connection to that disk before connecting the shed cable to it?
Have you checked the cable from the house to the shed is wired/working correctly using a Network Cable Tester?
I have connected it all up indoors, to rule out the long run of cat 6. Had the ap directly connected to a disc in the house
Ok, have you tried a factory reset of the AP?
Yup
Out of ideas now I'm afraid
I may have missed it if you have but have you connected the WAP to your router directly with a known good Ethernet cable and made a connection to the WAP without involving any discs?
Sorry, I should have already said this, but yes I have, tried to rule out all the factors first
I am still not clear, have you checked the disc that you are using to connect the shed is actually working when you connect an Ethernet cable to it. ie have you plugged a laptop into a known working Ethernet cable connected to the disc and made an Internet connection?
If that works and you say the AP apparently works the only thing left is the Cat6 cable.
Yes the discs all work and the ethernet point works with other devices. I think it's definitely some kind of networking clash....not sure if a wireless access point can be connected via a disc