Thanks everyone for your replies.
I will definitely get a proper test drive in the TTS before making a decision.
dr Dunkel – the truck space in the TTS isn’t too bad, especially if you fold down the rear seats. It’s not quite as big as the 135i, but it is sufficient for our weekend warrior or slightly extended road trips.
I know you can tune the heck out of the 135i with BMW performance or Dinan parts, which would likely remedy the suspension. I thought the M1 was just a rumor? If not, I might just have to wait!
I have a regular TT, just to comment on the luggage space. It is quite accomodating and with the back seats down I can get 4 tyres/wheels in the back
EVO in the UK had a 135i as a long term test car with the intention to tuning it to beat the M3 lap time on their circuit. The experiment only lasted a couple of months and ended abruptly as when they added all the BMW performance bits (power, suspension, wheels, tyres ect.), while it felt better to drive it was actually slower around the track. The 335i seems to be a better balanced car but I suppose you have to pay the extra cash for it.
While the TTS may be down on power vs the 135i it is ~140kg(300lbs) lighter so is a match up to 160km/h and in gear, however at high speeds the 135i will pull away. The less weight + standard mag ride also allows the TTS to respond better in direction changes ect.. and results it in being quicker on a track.
BMW 135i Coupe (E82) vs Audi TT-S Coupe - FastestLaps.com
Also, here is another comparison article to look at, it is the 135i against the 3.2 TT but you may pick up some more information
1-Series Coup vs rivals | Car Group Tests | Car Reviews | Auto Express