OK - On full right-hand lock there a distinct metallic rattle eminating from the engine bay - actually sounds very much like an exhaust heat shield may be loose and is just catching on the steering arm on full lock? Stops when full lock is off. Any more ideas? I'll check this weekend - just wondered if anyone else has had this? :idea:

Could be a loose arch liner

I'd waste no time, jack it up and get that wheel off.

The problem is most likely visible.