Problem solved thanks to WNW.
There is a close up of the leading edge of A2450 on the WNW website which explains all. The fuel line runs from the base of the gravity tank to the leading edge,turns left along the LE for a bit and then runs back under to join up with the strut.
If anyone else out there is doing A2450, don't forget to cut away the cowl in front of the front cabane strut to accommodate the fuel line, as per the photo on page 7 of the instructions. I did and found it a bit of challenge to get a neat finish retrospectively.