All of this is quite funny!! A few years ago when I bought my Rover 75 Connoisseur in dark blue, after I had had it for a few weeks, I began to wish that I had got the higher spec jobby and so, I started to look around for one and luckily one turned up, exactly the same colour as mine. There were a lot of differences mind, leather seats being one of them, different alloys, computer etc etc.
Went off and did the swap, got it home and the car was used on a daily basis by both of us but, it took my wife, friends and family close on 4 months before they realised that I had changed it!!!