If your area is prone to freezing, yes you should wrap the pot.

Just the pot, if the temperature drops below zero degrees C day and night for longer than 4 or 5 days,to prevent the soil freezing. The tree itself is hardy in the UK, its just the risk of damage to the roots from freezing if kept in a pot. It will need to be transferred to the ground at some point, its not something that can survive in a pot for a long time.

Thank you that's valuable information. Is fleece OK to wrap the pot in?

Well, sort of - if it gets very wet, its not a very good insulator - layers of bubblewrap or fleece and bubblewrap, remove to dry off when its milder. Its pretty unusual to have temperatures below zero day and night in the UK... it'll help to stand it in a sheltered spot, maybe up against a house wall where it might get some sun in winter.

The worst enemy of Cupressus sempervirens are gale force winds which tend to 'splay' out the foliage and destroy the symmetry of these beautiful trees

Aside from that , they are quite hardy .