Registered large letters are usually cheaper than Parcel Post and will give you a tracking number. The exception to "usually" occurs if the item is over 250g - Registered Post actually is more expensive than a 500g parcel in this case.

One annoying thing about Registered Post is that a lot of times they don't scan it until the item has finally been dropped off, so for all of the time in between, the tracking details only shows the post office where the item was lodged and nothing else for up to a week in some cases! I have also had a couple of items still considered "in transit" despite being given positive feedback from the buyer after they received their item!