Depends what they mean by "out of balance". I'm assuming that means that one side is braking harder than the other ?
Given that you haven't looked at them yet I would give them a basic service regardless of whether the calipers are misaligned or not - the ones in my V6 are misaligned to the point where the left hand one is very close to touching the disc and neither side was working at all (the rear of the car was lifting right up under braking) but after a simple service they passed the MOT without comment and they actually work perfectly fine. (braking is excellent, no lifting at the tail under hard braking)
What I would do is remove the pads and make sure the pads are not actually rusted to the caliper, (some were in mine) clean up the gap between the pads and caliper so they don't jam against each other, put the pads back then squeeze each piston right back and push it out 4-5 times, I do this with the pads in place by squeezing between the caliper block and the tab at the top of the pad with a pair of adjustable pliers (the sort that has several slots for the pivot to go into) and using the brake pedal to push them out again.
After that bleed the brakes thoroughly and you'll be amazed how well mangy old pads with misaligned calipers can work.
Free movement of the pistons and pads is the key, along with absence of air bubbles in the brake lines.
Yes if the calipers are misaligned due to rust you'll want to get that done one day...but unless its nearly touching the disc I wouldn't fret about it.
