At present WSAD pans the camera while the arrow keys can be used to navigate the menu/buttons, in a similar way to how on gamepad you can move the camera with the joysticks and navigate the menu with the D-pad.

I haven't used AutoHotKey before but googling it looks like you could do something like "send {WheelDown 1}". It probably wouldn't be too hard for me to for example make "pg up" and "pg dn" do the scrolling too but I'm not 100% sure I understand the problem. Eventually I'm hoping to allow it all to me custom mapped (which Steam wants me to do as well).

Well, I am kinda a 'black sheep' when it comes to WASD.
I grew up using the arrow keys, and never used WASD for scrolling in games. So I find WASD very uncomfortable.

I have a script set up with AutoHotKey running, where arrow keys do the same thing as WASD. But, for some reason if I hold down an arrow key for a few seconds, the scrolling gets stuck going in one direction.
I'm sure it's something to do with the way I have the script set up, as I'm not an AutoHotKey expert.

If you do ever get a chance to implement it, one way I was thinking is to have a toggle in the Options which overwrites the arrow keys to do what WASD does.
I typically use the middle mouse button to rotate the screen, and wouldn't be missing out on the lost arrow key function.

I understand if you don't feel it needs to be implemented, because, as I said, I'm pretty much a black sheep as most people are comfortable with WASD.

Here's the script I run in AutoHotKey, for my personal use, just in case you wanted to see it hehe:
----------------
#UseHook
SetKeyDelay 10000

up::w
down::s
left::a
right::d

rcontrol::r
----------------

I definitely want to allow re-mapping in the future but there are a few things to change in my code first. For example "R" rotates objects but also brings up the research menu if your mouse isn't over an object, but it would be weird having a different key do both if it wasn't "R" (although R probably only makes sense in English...)

Maybe also try

#UseHook
SetKeyDelay 10

up::Send, w
down::Send, s
left::Send, a
right::Send, d
rcontrol::Send, r

I just thought I would also mention you can pan the camera around by holding the right click mouse button.