Not sure on the controller alone. But yes you are correct all you need to do is swap the module and add an external GSM aerial. This is because the premium uses SAP profile and basically slaves your mobile to save on radiation and battery power. So the contoller needs an external GSM aerial, and the cheap antenna's that come with the units on ebay do not work. They throw a fault code in vagcom that cant be cleared until you fit the oem antenna and will get no reception on these, or a very very poor one. This is due to an impedance mismatch in the unit and chaepo antenna.
I am using an OEM VW R32 sharksfin that has GSM,GPS and Radio all built into one antenna. Also if you go down this route you will need to make up some fakra to fakra female extension lead to run from the module under the seat.
Lastly, the premium unit only supports mobiles with the SAP profile. So basically just newer Nokia's!