yes I forgot about all the power steering bits, I guess by the time you pull it to replace seals/pistons etc, you may as well put back a new rack, or a remanufactured one at least.
Apparently this place is good, not sure if there is a good place in the UK.
New rack price from Audi is ridiculous, close to £1000.
http://forums.quattroworld.com/a8/msgs/44931.phtml
also check out quattroworld they covered a lot of rack problems. could be inner tie rod ends?