Well Adrian
i think you answered your own question really hehe
mine does this as well.. it sorta drops into neutral while coasting but as soon as you put the pedal to the metal again she gets in gear and goes
my opinion.. if all three of yours did this... i would say it's normal.. mine does it too...
signs of a wearing transmission can be the delay from going from Park to Drive or Park to Reverse
max limit from Park to Drive is 1.5 seconds
max limit from Park to Reverse is 1.2 seconds
just check your trannie fluid and make sure she's still nice and red... change it every 2nd oil change and i think it's 20,000kms or whatever is recommended by your local parts dealer for your transmission filter and you'll have a happy transmission for a long time
so tell me why you've owned so many mk3's hehe... got any pics