audi brake problem

[Muffster]

Hello fellas,
ive got a problem with the front brakes om my A4 TDI 130. Basically when the pedal is pressed i get a metallic clunk coming from the front OS caplier. It doesnt do it all the time and depends on braking pressure. I have changed the pads twice and they are wearing unevenly but i cant see what the problem is. The outer pad seems to be loose and the clunking noise is happening as it moves around in the caliper when the pedal is pressed.
Does anyone have any ideas please, its driving me mad.
Many thanks,
Muffster.

[Muffster]

No mate, the discs are quite new.
Cheers,
Muffster.

[Muffster]

Ok thanks for that mate, i will give it a try. I thought it might be the aftermarket pads which were giving me the problem. New from audi they are 67 quid!!!
Thanks,
Muffster.