Please Help Brake pads and disc issues

My 2005 A3 Sportback visited my local Kwik-fit today for rear brake pad change and cambelt change. Cambelt change was all ok, but got a call as they were looking at the rear brakes saying the rear discs were 'severely worn' and they had to be changed immediately. The car had gone for service at Audi at New Year where nothing was mentioned about the rear discs (except rear brake pads were 85% worn, hence being changed) so phoned Audi to query this as was quite concerned the discs had gone from being OK to dangerously thin in 4 months! They said this was quite normal and they would likely have been fine when it was serviced - is this likely or are they fobbing me off??

At service I was also told the front pads were 60% worn but asked Kwik-fit to take a look today and they told me the pads were pretty much new and were nowhere near 60% worn! And that the front discs were also fairly thin but still OK for now.

So someone is telling porkies and I don't know who to believe?! Does anyone have any input into this?