Thanks HJ, that Presonus looks like it'll do the job - still blows my mind how cheap interfaces are these days, would have been looking at the sharp end of £300 for something similar 'back in the day'.
I'm not looking for particularly high production values for this, so camera wise I was going to see how it turns out with a GoPro 8, alternatively I have a Canon 600D which is getting a bit long in the tooth but produces good 1080p video, and if it really comes down to it I can fairly easily get intermittent loan of a 5D - but I'm hoping either of the other options will have it covered.