I don't know what the vet resources are in Scotland, but I do suggest you speak with your vet about a referral to an internal med specialist. If an ultrasound has not been done, I would ask about getting it done. There could be a growth and that is the only way to know. I did have a pup with a growth on his pancreas. There was nothing we could do but watch it closely with repeat ultrasounds. Three bouts in 6 weeks is a lot ... I wonder if perhaps it is just chronic and is not clearing up. A specialist may have some other thoughts/ideas.
As someone posted, pancreatitis can be deadly. I strongly suggest you get to a specialist sooner rather than later.
You say your pup is on a low fat diet. Honestly, that is about all you can do and avoid giving any treats! I only use treats occasionally and usually just a small piece of sweet potato.
Welcome to YT!
Please keep us posted on your pup.