Clio - 11mm Allen Bolt Wheel Nuts

Hi



I have a Clio 172.

Started to change the rear wheel bearing/disk today however I have been foiled at the first stage.



It appears that the Wheel Bolts are 11mm (est) Allen Bolts. Has anyone else come across this? I have never seen Allen Bolts used as wheel bolts (and no it is not the plastic fake allen bolts holding the cover on)



Any idea's where I can obtain a 11mm Allen Key suitable for removing wheel bolts?



Thanks

Freddy