What is the wear limit for brake discs UK?

Over the past week it has developed rumbling from the NSF, she dropped it off at Fiat this morning and surprise surprise they are recommeding replacement discs/pads.

Now, I'm well aware that they are consumable items and such will have to be replaced eventually but after 25k? Considering we are still on the first set of tyres gives an indication of how the car has been driven.

Several things in the conversation with the service dept. irked me. First he tried to claim that he would expect them both to be replaced after 18k routinely so we have done well out of them so far. Secondly when pressed on how much of the pads were left he back-tracked and said it was only the discs that were 'heavily pitted and scored'. And third when I suggested that it was a bit strange that the discs wore out before the pads he once more changed his tune and said it was down to 'corrosion' or possibly 'a stone stuck in the pad causing the discs to become scored.

Shifty.

A quick visual inspection through the wheels revealed perfectly smooth discs with only a small lip having developed.

All thoughts and abuse welcome

My wife has a Fiat 500, it has been owned from new and has covered 25000 miles in 20 months and is generally driven nice and slow (too slow!).Over the past week it has developed rumbling from the NSF, she dropped it off at Fiat this morning and surprise surprise they are recommeding replacement discs/pads.Now, I'm well aware that they are consumable items and such will have to be replaced eventually but after 25k? Considering we are still on the first set of tyres gives an indication of how the car has been driven.Several things in the conversation with the service dept. irked me. First he tried to claim that he would expect them both to be replaced after 18k routinely so we have done well out of them so far. Secondly when pressed on how much of the pads were left he back-tracked and said it was only the discs that were 'heavily pitted and scored'. And third when I suggested that it was a bit strange that the discs wore out before the pads he once more changed his tune and said it was down to 'corrosion' or possibly 'a stone stuck in the pad causing the discs to become scored.Shifty.A quick visual inspection through the wheels revealed perfectly smooth discs with only a small lip having developed.All thoughts and abuse welcome

I've just had my rear disc replaced with genuine BMW parts. Mine was getting a little worn and with the wear pattern on it I didn't want to put a new set of pads on on their own as( pads were almost worn out) I thought they might take a while to bed in as the disc was a little dished.
I had the main dealer do the work as the bike was in for a new fuel strip to be fitted, plus I get a warranty on it as it was fitted by BMW.
I was also wary of taking the old disc off myself as the bolts are most likely well bedded in with locktite. So didn't want to cock it up.
Rear disc, new bolts and BMW pads Inc fitting was a little over £200.00 . I didn't think that was too bad. Another £900.00 for the fronts to be done sounds a little bit extortionate to me.
Anyway I got 110.000 miles out of 2 rear discs so it's not really that expensive. Second set of fronts on the bike have still got loads of life left in them I expect them to last for another 30.000 miles or more.