Have a really close look at the springs.
I experienced a similar knock and it turned out that both front suspension springs had snapped. The breakage is hard to spot - they went on the bottom (last coil) which is encased in a plastic sleeve. If you pm me your email address I'll send you a picture of the broken springs so you know where to look.
My car is a 2010 Clio 200 Cup with 45k miles.