You can preorder them at OverclockersUK:
•Sapphire Radeon RX 470 Mining Edition 8GB (Samsung)—£300
•Sapphire Radeon RX 470 Mining Edition 8GB—£290
•Sapphire Radeon RX 470 Mining Edition 4GB (Samsung)—£260
•Sapphire Radeon RX 470 Mining Edition 4GB—£249
•Sapphire Radeon RX 560 Mining Edition 4GB—£170
Cards are backed up by a 1 year warranty.
The cards do not come with display ports so you will not be able to resell them to gamers.