I too am looking at having "cruise" retro fitted to my A4 2.0L TDI SE. The car is a 2008 July model.

Have become a little confused regarding price as my local dealer quoted £408 and a dealer a few miles away quoted £281.
The difference seems to be to do with a "slip ring" that is either required or not and my local dealer is supposed to be looking into this ( basically they don't want to lose me as a customer)

Hopefully I'll get a response soon, I can then post back with the findings.