hello murray the best way to move it is ask the new owner if you can move it when its dorement ie winter . very early spring /late winter is best as it can grow almost strate away though there are 2 viable slots . the other one is late autumn just after the leaves have dropped of the trees . this will probably suite you considering everything . the chances of killing it moving it now are quite high realy . when you do move it you want as much rootball and soil as you can reasnably get .rap it up even in something like a stringy hessian excuse my spelling as you can almost just replant it in the new garden without taking it of as the hessian will rot out . also dig a bigger hole bye double than the root ball . water the hole ie soak it realy well then when the waters gone put some good topsoil down or buy some multi purpous compost . then dig your plant up and move it to its new home strate away and plant it .its worth keeping a little dip wear the plant is after youve firmed and waterd it in so it tends to hold water . then as spring starts up water well for a year . after that water as you have been . dont forget to wrap it up this winter as including me a lot of people have lost there cordylines this last harsh winter especialy as you will be moving yours at a vulnrable time .