Main dealer I’m guessing. I had this for years on an Astra, every service in the 1st2 yrs they came up with this one (front pads/discs worn) and I ignored them 'cos I measured the pads regularly and I knew how long they lasted.
At about 70k I got them to eplace the cambelt (a good price at the tome) and they insisted on doing a safety check, at which they pointed out several things including (you guessed it) the front pads!
By this time I was well annoyed, got a micrometer,measured the discs, measured the pads, wrote to VX to complain about the garage (among other things they said the spare had 7mm of tread, it was 3mm! and the rear wiper was worn - it was brand new). Upshot was a loooong interview with the garage chains regional manager, and a free set of front pads and discs. Which my local garage fitted for me at about 100,000 miles!
I also had the same at kwikfit when the car went in for another item, free brake check blah blah blah. Halfords, later the same day, checked and found no problems at all!
You can see for yourself if the discs are corroded. Even if they are, my friends local garage always advised him to give his old jeep an italian tune-up on the way to the MOT, to make sure the brakes weren’t rusting. Worked a treat.
Context for cost? my local garage has just replaced both front calipers, and the pads, when one of the calipers started binding on my '07 NC (just turned 100,000 miles!). Total bill £399.42. They usually replace the pads for less than £100 each end, unless I ask for Mazda pads which brings the cost up to £100.