TT TDI confuses me.
If you don't want teh 135i or TTS your choice is:
I personally prefer the TT 2.0T to the 125i. The TT drives really well, especially for a FWD car. I think the 125i engine is a little souless and not very economical compared to the TT's 2.0T FSI.
The TT can easily be remapped to 250bhp if you fancy doing it too.
TT also likely to have better residuals.
123d is a fantastic car, great engine, but you need to decide - petrol or diesel.
Current: 2015 BMW 640d Coupe Imola Red with Ivory leather and 20" alloys
Previous: 2013 Mercedes C63 Coupe, 2011 Mercedes C350, 2010 BMW 135i Convertible, 2008 BMW 135i Coupe, 2006 BMW 335d Coupe, 2006 Honda S2000, 2003 Honda S2000, 2003 BMW 330Ci Convertible, 2001 Audi S3