Prongs are not allowed in Scotland, correct or not?
If you are training to walk, I would use a collar, clicker and treats. Teach them position. OR a harness specifically for training. But the more info I see come out about harnesses, the less I'm inclined to like them.
Some videos here on training your dog to walk on a "loose" leash. Generally a harness is "not" the way to go with an untrained dog, once your dog can walk well on a loose leash then you can use a harness. stop dog pulling on leash - YouTube