Yes, it is quite rare to find unregistered land these days but it still exists.
The difference is that the ownership is not registered at the Land Registry so the owner has to show that they have the right to sell the land by producing evidence that they own it such as the conveyance.
The purchasers solicitors will apply for a first registration at the Land Registry when they register the new owners after the sale is completed.
As such as a consequence of the sale the land will become registered.
I hope this helps.
If there are any further points please reply and I will be happy to respond.