To secure the phones at these low prices customers will need to sign a new 24-month contract.
The iPhone 5c features a plastic rear in a choice of colours – blue, white, pink yellow and green – made from hard-coated polycarbonate and reinforced with a steel interior.
It also offers 4-inch Retina display, the same A6 processor as the iPhone 5, a 8MP rear camera and Bluetooth.
The higher spec iPhone 5s comes in silver, gold or space grey aluminium, and 64-bit A7 chip.
Apple claims the handset is 40 times faster than the original iPhone and offers 10 hours of talk time over 3G and 40 hours of music playback.
In a bid to boost security, the iPhone 5S also includes a fingerprint scanner in the home button which allows the user to lock the device and be sure that only they can access their data.
Three says customers buying either model will gain access to its 4G network when it launches in December.
In addition to the new models, Three will be offering the iPhone 4S free on a 24-month contract.
“We are very excited to announce that the much anticipated iPhone 5s and iPhone 5c are now available on our network,” said Thomas Malleschitz, marketing director at Three.
“iPhone 5s and iPhone 5c, along with our commitment to provide 4G at no extra cost, means that our customers can look forward to an even better network experience.
“We will also continue to offer all-you-can-eat data, so customers can truly enjoy the full capabilities of iPhone 5s and iPhone 5c without having to worry about exceeding their data allowance.”