Fabia 1.4 Brakes

On my Fabia 1.4 TDI with ABS fitted, when applying the brakes lightly for say 5 seconds and then having to apply a harder pressure in order to stop more quickly, I find that the brakes are very poor and not capable of stopping in the distance available. However if I quickly lift off the brake pedal and re-apply, I have excellent brakes and can stop in half the distance, this has always been the case since new....Someone has suggested that it is a common fault because the vacuum servo after it's initial application, has not replenished the vacuum....Has anyone else experienced this?....If so, is there a fix to get maximum braking on the first application?....Any help most appreciated.