IMPORTANT: Have done some further BP programming, I have worked out that the only thing wrong with my initial Blueprint was that the Trigger Volume was smaller than the TargetPoint the NPC was running to. This means that the Trigger Volume was never being overlapped. That means, for anyone reading this now, that my first BP is correct. It was my placement in the level that was wrong. I could have got my method to work perfectly, if I had known this, and just increased the size of my trigger volume. Sorry! 
I have a pawn called BasicAI. He runs to a TargetPoint with a TriggerVolume around it. How do I get the OnActorBeginOverlap event for the TriggerVolume to fire when he reaches it?
The event is set up to fire if the Player enters the Volume by default, and I can’t work out how to change it to the Pawn. I’ve tried connecting the OnActorBeginOverlap event’s Other Actor node to Cast To Basic AI, but to no avail.
If someone could let me know what I am doing wrong, I would be very grateful. Also, points!
EDIT: Here is my new BP for the successful patrol, after Raiden’s help. It doesn’t use the onactorbegineoverlap, but actually serves my purposes better.
So in simple terms you want the BasicAI to move from Point A to Point B, activate a trigger and move back to Point A or another Point?
Actually, I’m using the trigger to send Basic AI to Point C (this is supposed to be the NPC’s patrol route). I have no idea how inelegant my solution is, so if you have a better idea, I’d welcome it.
I hope this helps what you are trying to achieve. I have just created a simple patrol route for an AI bot I am using. What happens is I hit the trigger and the bot moves to the first point which in this case is point 2. After 0.2 seconds he then moves to point 3, then again after 0.2 seconds he moves to point 4 which he then moves immediately to point 2 again but only because I forgot to put a delay at that point.
In short activate the trigger and he moves from point 2, to point 3, to point 4 and then back to point 2. Is this what you wanted?
P.S Don’t forget your NavMesh
I have done this in the Level Blueprint.
Don’t worry, I didn’t forget my NavMesh.
This certainly looks like it. Which blueprint is this on?
Right, I’m in a bit of a quandary. You haven’t quite answered my question. I asked for a way for a pawn to trigger the onactorbeginoverlap event, and this doesn’t actually do this. This just sets a time limit, and changes the destination once that limit has been reached. This means that if the pawn is stopped (by, say, my character speaking to them for the required amount of time, they will no longer make their way to the destination, but the next one (or even the one after that, depending on how much time was lost).
The thing is, if I do what I want, with the overlap event, I’ll have a level of NPCs walking around, with clockwork precision. If I stop one of them, that would throw a spanner in the works as they would fall further out of synch with each other, and the beautiful edifice would slowly fall apart. I would need a way to reset their patrols automatically. Which you’ve just done!
So the quandary is: you’ve just solved my current problem, and the one I was about to have, but I can only accept your answer once. Thank you, so much.
I’ve posted my new BP in the original question, which is the same as yours, but with the Get Controller added for each Simple Move to Location.
Hey Jezcentral-
It seems that was able to help you solve your issue. If this is correct I will be closing this post as resolved for tracking purposes. If you are still experiencing the same issue that you originally reported please feel free to respond to this post and we will investigate further.
Cheers
