I have got an audi a3 and before i purchased it somebody else has retro fitted the audi RNS Sat nav/media, but my AUX port near handbrake doesn't work and also i have to keep re scanning for radio channels when save them and got back to them they are greyed out !! , i have tried to look how to resolve this but it all seems to complicated !?? anywhere in manchester i can take it or anybody know an easy fix ???

Without looking at it I cant say for sure but sounds like the retro fitter has mismatched the red (LIVE) and yellow (ACC) wires, redoing this should solve the radio issue. As for the aux, is it connected at back of stereo, should be a blue connector. 

 

I'll take it out later and take a picture of the back for you