not so diddlydo - see what I did there
'Under EU Block Exemption legislation, which has been around for many years now, a manufacturer cannot force a buyer to have their car serviced by their official dealership network, and cannot refuse to honour a new car warranty simply because a car has been serviced elsewhere. However, a manufacturer does have the right to set a servicing schedule which must be adhered to'
It is always attractive on resale to have a wanufacturers service record. If you sold it back to audi you may/may not get a lower price quoted for it.