I quite like the Q30 with it being a hatchback. I can't see anywhere on the ad's saying that they have DAB though. Fuel consumption and VED is better on the C Class.
Definitely food for thought.
The Q30 is based on the same platform as the A-Class Mercedes. The 1.5d engine is the same as that found in the A-Class too (which is a Renault one of memory serves me correct).
There is a 2.1 sport version though rare.
The Q50 is based on the Nissan Princess platform, so the same as the 350Z and the Skyline. In fact they market the Q50 as a skyline in Japan where it’s from. Engines in the Q50 range are all diesel.
In terms of radio, the Q50 offers a twin screen with DAB as standard. The Q30 has a much smaller single screen. Should include DAB though from what I’ve seen.