We read that the switch may only be a bit dirty and that it may be restored to working order easily. So we bought some 98% isopropyl alcohol from Maplin gave it a go and it worked, this is what you do.
Switch the iPhone off. Then use 98% isopropyl alcohol (don't use anything else as you may cause damage) on a cotton bud and work some in around the edge of the home button. Don't get any on the screen. Tilt the phone up slightly so any isopropyl alcohol runs away from the screen. Keep pressing and releasing the home button using the tip of the cotton bud to get the liquid well into the switch. Do this for a couple of minutes then dry it off and leave for about 10 mins. Switch the phone on and test it out. :)