Yesterday I've noticed weird cracks coming from the front drivers side of my Octy whilst driving. I've taken off the wheel and noticed that the brake caliper is loose, it's not coming off the mount but can be moved few milimeters from side to side.

I've tried to tighten the screws holding the caliper but 1 of the 2 bolt screws is turning with no end and therefore not tightening the caliper to the mount. I suspect the thread on the caliper mount is kaput.

Is it OK (safe) to leave the caliper held by 1 healthy and 1 bad screw? Should I replace the caliper mount? If so, where can I get it from without spending the earth?

What's the best way to go from here?

IIRC, some one should be able to confirm this too, the caliper is a floating design and should be able to move side to side as there is only a piston on one side of the caliper and the other pad is fixed

If the caliper has pistons only on one side then it will need to move sideways to keep pressing both sides of the disk as the pads wear.

I don't like the sound of the freely spinning screw - I haven't had to go at my brakes yet though (I have the same car as you), so it may just be a pin to locate the caliper rather than a fastener.

Does the cracking noise get worse when you're cornering? Could be a CV joint...