Corroded discs?

Can't see any mention of corrosion in the manual, only:

h. a brake disc or drum insecure, cracked or excessively scored, pitted or worn

Have a look here:

It was only an advisory, bearing in mind the MOT is the minimum standard & that is a low standard, I've passed worse then that ! My advise to customers is wait until the next brake pad change & then replace pads & discs.

I can't pass comment on the face of the disks. They look as if the car has had longish periods not moving, or you may not do enough miles or you break very gently ...waffle can go on.

There is one tell tale sign that you will soon need new pads, on the first image (and on the other two) you posted it seems as if the outer lip of the disks is touching the metal backing of the pads. You can't have much pad left.

The key is if the disks are thinner than the manufacturer's spec. As another post suggested, as soon as you need pads get disks too.

If it helps a little. Charles

What's the car? Someone here will tell you whether that £450 is reasonable or not.