Hi Lodgey...
If I'm right it's the feedback hose to the expansion tank(?). These are a a dealer part (Will set you back around £15). When mine went (at about the same point you indicated) I unclipped it from the radiator etc and ran it across the top of the engine acoustic cover (as it was a little shorter than before) and connected it with the existing pinch clip. Cable tie it to some other non-moving parts to stop movement and cover it with duck tape where it runs over the acoustic cover to stop any abrasion from the bonnet etc... This lasted me for about 2 months before I got the replacement hose.