Nev, I found an aceteylene one at the tip and it fiited into the 8.5kg BBQ bottle, the thread pitch is the same but the diameter is slightly larger. My new reg only goes in a little before it doesn't feel right but the old worn one seems okay. My neighbour got his to fit by spinning the nut with his wire buff wheel on the thread until it went in. Still works on both bottles. I have just built an oil burner which run great on gas aswell if you need any ideas made from inch water pipe.
Brock