Just in case anyone needs to take apart the shifters on these because of stripped grub screws, I'll detail the process.
First, you'll need to remove the two hex bolts holding the lever on to the handlebars. With all of this, be super careful to not drop them and put them somewhere safe.
When you've removed the hex bolts (M4 & M2), you have two options - one, you 'push' up the fixed metal mechanism against the spring to expose the back of the grub screw. From there, if you're lucky, grab your 2mm Allen key and remove the bolt, and flip it so the non-stripped side faces outwards, and it's 'job done'. If however you're unlucky like I was, and strip both threads (these bolts must be made of playdoh), you'll need to drill it out. As my springs popped out, I did this without the spring mechanism in place.
It was pretty straightforward to drill out the grub screw and replace it with a 2mm grub screw from Amazon. Putting it back together is the tricky part.
This is the important bit as far as the springs and mechanism goes - thick spring gone on the outside, followed by the fixed metal lever. There's a plastic tube that runs through both of those, and a smaller plastic tube runs through the thinner spring. Put the thick spring in, followed by the fixed metal lever, then push the spring down and carefully slide in the plastic tube. Repeat then for the thin spring and smaller plastic tube. Then your lever should be reassembled.
Be careful, take your time.
I'm sorry I didn't take pictures of the process, but if anyone ever runs in to this issue where they strip the grub screw, get in touch and I'd be happy to help out. It's a pain in the arse if you stuff it up, but it's certainly fixable with a bit of patience and elbow grease. I'm glad I didn't buy a new shifter.