I have just gone from stock to non res catback, and I absolutely love it. I am in my 40s so don't want a really loud exahust. The Milltek is just spot on - just a bit louder than stock, but with loads more character, especially when you put your foot down 
That almost has me sold but with limited £'s a new one is just too much.
The demand for pre-owned means a near hourly check on the for sale section before the vultures pounce lol!!
Why not stick a post in the "wanted" section? You should then get first dibs if someone is selling their GTi and wanting to take off a Milltek.