I just got it for display purposes and don't really intend to try to use it at all. But, from what I understand, the Six 16 film is not really something you can get anymore but one of the larger format films can simply be cut to fit it.That's not even close to my area of expertise so I wouldn't take my word for it but you might be able to find some info on Google.
616 hasn't been made since 1984. I think B&H Photo are the only people selling it at a close to reasonable price. $15 last time I checked, which is about £10. Then there's processing. Probably have to do it yourself with an older tank that supports 116 and 616. So the camera is still quite usable if you're prepared to fork out a little bit more than usual on film.
I have a 616 box camera that I can run 120 through. It requires spacers to hold the 120 in the middle as the 616 was wider if I recall right. I used old plastic 120 spools cut up and re purposed as spacers for the 120 spools with film on them. Worked very well and was smooth as silk running through the camera. The hardest part was the spacer that engages the actual winding gear of the 616 camera. It required some more thought and effort but not much.
I asked a friend who specializes in old-school film cameras and the 120 is what she recommended as well. I'm a bit hesitant to try it though and i'm not even sure where I could find a lib that would process it. it's been so long since I've used film that the whole notion of anything other than digital for actual shooting purposes has become a foreign concept for me.
You could find a tank and chemicals online and do it yourself in B&W easy enough then scan the ginormous negatives yourself. I built a dusty little darkroom in my basement. The gear to make one is cheap now if not free if you just look around craigslist, garage sales and so on. We have a large camera shop/lab that will still process 120 so I'm sure Pittsburgh would also.