@SarahGen-- I don't think that jacket potatoes are ever parboiled. They're baked directly and it can take up to two hours for them to be fully cooked.
If you like the skin to be crispy, then put them directly in the oven. Make a few punctures in the potatoes with a fork though. If you like the skin to be soft, then you can wrap the potatoes in aluminum foil.
I've traveled a lot for my job and I've encountered jacket potatoes in basically every country I visited. The toppings are the only part that changes. For example, in Britain, they eat jacket potatoes with baked beans which is not unheard of here in the States too.