Hey mate,
I've reloaded the file again. This was literally the first file I've ever made and I've come a fair way since then. I ended up getting a 3d printer and it was the first thing I printed. The software repaired it because the first print failed, but it filled the holes where the screw and washer fit. I just drilled them out and it did the job. Let me know how you get on.
https://file.io/YVvgzURZrHzD
This is still the original file untouched.
@jamesinc Still unable to upload a .STL or .OBJ file.
Thanks and all the best.