I know it's a bit later than the initial post but I figured I would give my thoughts of your list of potential cars:
1 series coupe BMW 125i or 123d - Reliable cars, but very expensive to fix/service. You also have to face the reality that they aren't the top of the range (1M) model - and people generally don't have a high opinion of those who drive BMWs/Audis (stereotypically speaking).
Z4 3.0 SI - Once again, I also considered this before buying my Zed - but one great thing you get with the Zed is the timeless styling due to the fact that they will not make another '350z' whereas they update the Z4 and it will therefore age.
Honda Civic Type R - VERY dependant on which model you're thinking about: If you get the EP3, it is a phenomenal car! My brother has one, which I drive occasionally... handles like a dream, sounds great - a real drivers car! However, not as powerful or fun as the Zed. If going for the FN2 (newer model) all I can say is: AVOID LIKE THE PLAGUE. It's slower than the EP3, feels sluggish, understeers like a b*tch too! Nicer interior, but overall, they cheaped out on it and as a result it's terrible.
350Z GT - I am the owner of a 2004 350Z GT pack and I gotta say, fantastic car. I actually had a poll with it and the other options with women before I made my purchase. Women are the best judges of style - The contenders were Mazda RX-8, Alfa Romeo Brera, and 350Z. Despite the Brera being a great looking car, an overwhelming majority of women sided with the 350Z.
Audi TT Mk1 sport or TT Mk2 VR6 - Hairdressers car