Will I need to move out of the property whilst the work on the loft conversion is carried out?

No, all work is carried out externally and all materials pass through the front of the roof, nothing through the house. The only time we would need to enter the house is when we cut through the ceiling in order to fit the new stairs, usually around week 4, but at this stage most of the loft has been completed and all of the rubbish taken away.