weed control fabric

Weed control fabric is unlikely to kill of nettles at all - if its an area that you're not using for some months and don't want to plant yet, cover with thick black plastic sheeting, anchored down tightly, to exclude all light and moisture. Otherwise, dig out the nettles, or, if you don't want to plant the area, treat with something like a heavy duty path weedkiller, then lay the fabric.

I only got rid of nettles by digging them up as they can run underground a long way.

Agree with both the above, what are your plans for this area? is it to be planted out at some point, if so then yes cover most of the area and then concentrate doing a section at a time, useing a sturdy mathook, grub all the roots out, julien.