How does M135i compare to 125i / 125d?

[Trailhead]

Drove a friends automatic M135i today and what an absolutely fantastic car it is. Beautiful noise, great fun.

The car would be an absolute licence loser for me, so I am considering the idea of an auto 125i or 125d instead.

Does anyone have any experience of these cars? How do they compare?

The best answer would be if they were just as fun but slower, or at least make you work a bit harder for the higher speeds.

As an aside, does anyone know if the speed can be limited on the m135i?

[Trailhead]

You guys are doing a bloody good job of twisting my arm towards the M135i.

Argh!

Is 37 mpg actually realistic at 70mph on cruise control?

I may try and sort a test drive of the 125d and compare it to my M135i hoon to help the decision along somewhat.