A car is never a rational decision unless you buy a cheap 1.2 liter Mazda or Ford ... . The 120d equipped with ALL the possible options will be more expensive than a 'standard' M135i .. but i only picked the necessary options like the M-pack, electric seats, satnav and that blue color ... no need for 1200 Euro headlights or 18 inch wheels.
i'm not really sure. Off course you could as well opt for the new MX-5 Miata ;-).