Phil-E30 - you sound like I felt when I went ahead and paid what I thought was over the odds for my car - you'll likely find other cars that you think might have been better buys and then prices which seem at odds with what you paid - and I still keep looking!
However - unless you feel you've been dreadfully ripped off - and from what you can read here on the forum you seem to be ok - then you begin to feel good about your purchase as you enjoy ownership. Then a few years on depreciation will eat up any money issues anyway.
Finally remember that you have purchased a lot of car and performance for the same amount as another person loses in depreciation when they drive their new(er) car out of the showroom. Enjoy your Zed!