The first photo was shot above the house towards the SW, so I missed the bottom half of the core that night.
The second photo is a panorama and the Milky Way in the left is looking towards the SW which is where I was expecting it to be (based on Stellarium). It was a relatively clear night with the aurora being very active.
Some photos I can edit it reasonably ok, but with others I struggle with, even when I am out of the light polluted areas. The area where I live has relatively lower light pollution based on maps so should be fine to get a semi-decent image. The difference can be seen in the images below, both taken with the same lens. The second image is a stacked vertical panorama with 3 horizontal shots.
Is it normal to struggle with finding a balance between noise and det
Ah, my mistake. I would have thought if it's dark enough to capture the aurora that well, then the milky way would show up more clearly.
How many images if you stack in the second one? I guess it's probably just light pollution, even if you shoot from a low light polluted area, if the camera is aimed in a direction where there is some glow it can wash out some detail and colour. As for noise, I don't know how well the 70D handles it? I know my 60D is pretty bad at 1600 and pretty unusable at 3200. For astro I always use my Canon EOS M as it very usable at 1600 and not too bad at 3200.
Also, what time are you shooting at? Being up in Scotland you're probably only getting a couple of hours of truly dark hours during the summer. Even here in Sheffield it doesn't stay properly dark that long.