We where all just discussing this the other day.........J.r.t are actually a breed notorious for there later development in early toilet training, as with some other terrier type breeds.
It's important, not to allow the puppy to have access to any room without u there to help correct and guide the passing of the motion, e.g, a smaller area is always the best place to start when toilet training, so basically a crate is the better option when u are not around and for bed, and watching for the signs, i.e squatting, when u are there, so u can break the motion, by picking the puppy up and taking it to the toilet area, and giving a praise and command, i.e wee wee pooh pooh
Also letting them out frequently, to get them used to a routine, and after every meal, if sectioned of in a smaller area or crated, always release them as soon as u return, carry them if need be, straight to the garden, so again, they know it;s crate to wee wee area, otherwise they will wonder around and piddle
Re training...try introducing some treat based short training sessions, and lots of fun play sessions, to wear him out