Brake Judder Returns - Second set of front disks!

[Marcosal]

My XV goes in for its third service at 33k miles and its 1st MOT. This car gets fairly light use but I am on my second set of front disks and they are also showing signs of warping. I contribute to the American XV site and they have reports of XVs being prone to this in the States. has anyone on here had a similar problem?

[Gambit]

Sounds like  the pistons on the brake calipers could be seizing but 33k seems low milage for that to be happening. But only thing I know that would cause the disc to warp underlight use unless the disc was of a cheap make. 

[Marcosal]

First set of replacements disks were fitted under warranty by my local Subaru dealer after skimming did not solve the problem, so the replacements should be the genuine article. The odd thing is that the brakes are fine when you first set off from cold and the problem gets worse with distance travelled not the number of times you brake. I regularly use the M40 between my home and the A34 Oxford turn off (about an hour) and after an hours steady motorway driving (less than 10 braking events) the brake judder is very noticeable. Whereas local short distance journeys with many braking events do not produce the same juddering effect.