New brake discs - thickness?

I am looking at getting new front brake discs fitted, and looking at eurocarparts I can get them cheaper then the garage I think. Eurocarparts brings up a couple of different thickness 25 mm and 27mm for a few £ differences.

Will both work? I am looking at moving the car on in 6 months - a year so was looking at getting the 25mm.

http://www.eurocarparts.com/brake-disc

Cheers