The distinctive "trunk" is formed from the stumps of outer leaves that die off over time. Date Palms will survive short exposure to -6°C, however if exposed to prolonged low temperatures around or below 0°C, the plants will deteriorate. Also, if the soil/compost you’ve planted them in becomes waterlogged, they'll also struggle. That said, these plants are known to thrive in the UK if well looked-after, and will become much more tolerant over the coming years as they establish. Make sure you protect yours in the early years and it will be fine!
Will
YouGarden Ltd