On page 121 of the manual there is a note that says:
Does anyone know how to do this with VCDS? I'm sure the dealers would try and charge me a bomb for it...Distance 3 is sot automatically each time the ignition is switched on. If you would prefer to have a different distance as the default setting, you can have the adaptive cruise control menu extended/activated by a qualified workshop.
On the subject of VCDS as well, is changing the settings with it in any way dodgy in terms of warranty, insurance etc? Is there a danger of things you've changed being overridden again at a service or anything like that?