What devices do you need for aerospace engineering? (e.g. iPad or Laptop)

I am thinking of using an iPad for notes and other bits and bobs. But will I need a laptop with decent specs as well in order to use CAD and other similar software or is that kind of work typically carried out on the department's computers?

You will need a computer (laptop or desktop of some kind) for undertaking course work.
To use software such as CAD or CAE you will need a computer with good graphics capability. Most laptops will struggle unless you’re prepared to start looking into the £1,000s for the computer particularly with anything computationally intensive (i.e. fea/cfd). However if you don’t have the budget it is standard for universities to have computers with engineering software accessible either on campus or in some cases through virtual desktops.
I personally also strongly dislike using any engineering software on anything other than a full desktop setup i.e. a proper 20” screen + keyboard & mouse but you can dongle these up to a laptop, particularly newer ones where you have one USB C plug and it syncs up everything.
I would recommend making sure you have a good laptop or a good desktop & laptop over having an ipad + laptop just from a functionality perspective but this is really personal preference.

How would a good desktop and an iPad be? That way you could get a good secondary (the iPad) to take notes but also a good machine for coursework. I’m also in the same boat of deciding and currently have a really good desktop. Any thoughts on this would be welcomed.

I think this would be solid, you could use your desktop at “home” & university machines for in campus.
The problem with this is without a laptop you will have a flexibility hole, particularly for working on campus “flexibly” (when you want to work with mates or during peak coursework season libraries can get full) or if you go to your parents for xmas or the weekend, dragging a desktop PC is a real challenge. So without a laptop you have to be aware of this hole
In general i personally would go with a laptop & desktop (over an ipad), ipads are really really great devices but I think they have functionality holes. Now i went through university making all my notes with pen & paper (nowadays it’s become more fashionable to use entirely digital tools).