Hi Lee
A plumber friend of mine recommended a product called Armaflex for lagging the pipes. He reckons its the best. As I have an extension out the back of my garden I had to fit the copper water pipe down the side of the extentsion to the new position for the tap. I covered the copper pipe with armaflex, wrapped it in duck tape and pushed it through a drain pipe from B&Q to keep in wate tight. I did it in Feb this year so havent tested it yet with the freezing weather we've had over the past couple of years. Time will tell.............!
One thing though...My Pa-in-law suggested changing the copper pipe to non mettalic flexipipe. That way, if the water inside freezes it will not split like copper pipe would as there will be more room for flexibility. If I have problems I will do that next year!