The driver's side (OSR) rear disc on my 2012 Combi Greenline has a series of circular ridges which stand proud of the disc and are rusted (so looks like they've no contact with the pads).  The remainder of the disc is clean and is obviously in contact with the pads.  Its also taken to squealing when moving off after standing overnight.  The squealing isn't changed by braking but goes away after a minute or so or driving.  I haven't time to remove the wheel and look at the pads but l reckon that they must have failed in some way.  The other three discs are perfectly flat and clean.

 

Has anyone come across something like this before?  The car has 29,000 km up and is going in for a service in a week's time.  I'd be very interested to find out if this is a known issue before being hit with a bill.

If they're as described, I'd say you've a funny pad. There may be a warranty claim here; otherwise expect to pay for 2 rear discs and a set of rear pads.

 

I can't comment further without seeing (real life not pics) the disc and pad.

Thanks - I reckon its faulty parts too but sometimes these things aren't straightforward.  I'll resist the temptation to remove the pad for fear of disturbing anything and will see what they say at next week's service.  I'll report back.