I’m hoping there’s someone else on the team with experience of craft fairs in Devon who can give you some suggestions...
But this Stallfinder website should be worth looking at. Let us know if you spot something of potential interest.
https://www.stallfinder.com/event/county/devon/0/It’s important that your craft is a good fit for the venue. It always a good idea to attend fairs that you are interested in participating in before you stump up the fee for a stall yourself. Ask yourself – 1, Does this look like a well organised event? 2, Is it well attended and well publicised? 3, Do the visitors look like the demographic that tend to be interested in your craft? 4, Is there already a glut of your particular craft, or can you fill a niche? 5, Are people who make similar stuff to yourself under cutting you or is there an expectation of a professional price for a professional product? 6, Do the stall holders look happy? Talk to them....
If you can identify why your first attempt was a “disaster”, you are now in a better position to make sure your next attempt is a success!
Other than that, I don’t think I can be much l help to you. I do open studios in Exeter and have had experience of one major art fair so far, which I did as a way of getting my work out of Devon.
Do let us know how you get on.