Bluetooth can't officially be retro fitted as the wiring is part of the cars loom. All cars have their own bespoke loom from the factory depending on spec. So when the dealer looks up the parts, the computer will tell him that they are not compatible with your cars chassis number.
The third party kits that many of us have fitted use an aftermarket piggy back wiring harness that just plugs into the radio loom and has another wire to the mic. They still require coding to tell the car bluetooth is fitted, but that is just a case of ticking a box on VCDS. If all you want is bluetooth, you'll get that job done for £250, not the £1000 that the dealers will rob from you for the Kenwood.
As for cruise control, I'm pretty sure it's listed as a dealer fit accessory, so there should be no issues with that.
